PRINCIPLES
OF
CROP PRODUCTION
1
Compiled by Madam FRIDAH.
INTRODUCTION
HISTORY AND DEFINITION OF AGRICULTURE
The early human beings were fruit gatherers and hunters. They also ate the fruits and seeds of certain plants. However, human beings lived on earth for many years before they began to practice Agriculture.
It is believed that human beings began to plant their own crops instead of simply gathering fruits about 9000 BC. The earliest crops they grew were cereals such as wheat, barley, sorghum and millet. Over many centuries, both crops and animals became dependent on human beings for their existence in a process known as domestication.
Human beings cultivate fields for the purpose of producing crops for their needs. Producing a crop involves not just cultivation, but planting the crop, caring for it until it is harvested and storing it is eaten or sold. In order for crops to produce good yields, the farmer requires good knowledge on how each crop grows and reproduces. It is also necessary for him or her to know about pests, diseases, soils and agricultural economics.
Agriculture is therefore defined as the art and science of crop and livestock production. As an art, agriculture entails; tilling of the land; construction of farm structures; measuring distances; machine operations; harvesting of crops; and marketing of agricultural produce.
As a science, agriculture entails; crop pathology; entomology; agricultural engineering; soil science; and genetics.
ROLE OF AGRICULTURE IN THE ECONOMY
a. Food supply.
Agriculture supplies adequate food to both the urban and rural communities ensuring a healthy population which spends more energy in other aspects of economic development leading to a wealthy nation.
b. Source of employment.
Agriculture provides direct employment to over 70% of the people of Kenya, as full time farmers, farm employees, and those in the agro-based industries. A section of the population is indirectly employed in the extension services, research stations, transport and industry.
c. Provision of foreign exchange.
Foreign exchange is the currency that is earned when various products are exported. About 7% of exports from Kenya are mainly agricultural products such as coffee, tea, pyrethrum, horticultural crops etc. when these products are exported; they earn the country foreign exchange which is used in purchasing raw materials, manufactured goods and servicing foreign debts.
d. Source of raw materials for industries.
Efficient agricultural production is necessary so as to provide the required raw materials for most industries in Kenya. Examples of such industries are the tea factories, maize mills, rice mills, canning factories, breweries, leather tanning and milk processing industries.
e. Provision of market for industrials.
The final products of industries such as agro-chemicals, tools and machinery find their market in the agricultural sector i.e improved agricultural production requires use of machinery and agricultural chemicals.
f. Source of money or capital.
When a farmer sells agricultural products, money is earned and used in purchasing farm requirements such as pesticides, capital goods such as pangas, jembes and wheelbarrows. The money obtained is also used to help the farming community in improving their standard of living.
MAJOR CHALLENGES / PROBLEMS FACING KENYAN AGRICULTURAL SECTOR.
These facts about Kenyan agriculture sector possess a number of challenges to the sector. The major challenges can be summarized as follows:
1. Climate change.
The effects of climate change have been felt mostly by the farmers especially due to dependence on rain-fed agriculture. The changing and unpredictable raining seasons has greatly affected their ability to plan their farming activities. Areas which received adequate rainfall now receive insufficient rainfall reducing the land that can support agriculture.
SOLUTION: This brings the need for more exploitation on irrigation farming especially in arid and semi-arid areas.
2. Poor infrastructure
Poor rural roads and other key physical infrastructure have led to high transportation costs for agricultural inputs and products. It also leads to spoilage of perishable commodities during transportation. This causes high losses to farmers.
3. Lack of capital.
Most farmers cannot get access to credit facilities since most commercial banks require collaterals such as tittle deeds which most farmers may be lacking thus have limited access to credit facilities. Also high interest rates imposed on these loans make them unattractive.
4. Pests and diseases.
Pests and diseases have continued to cause a lot of losses to farmers. This is caused by lack of information by the farmers on how to control these diseases. Maize in the eastern province have been affected by afflatoxins in the past due to lack of proper treatment and storage facilities.
SOLUTION: extension services can be instrumental in helping reducing pre and post- harvest losses caused by affatoxins.
5. Agricultural extension services.
The agricultural sector extension services plays a role in disseminating knowledge, technologies and agricultural information, and in linking farmers with other actors in the economy. It is one of the critical change agents required in transforming subsistence farming to a modern and commercial agriculture to promote household food security, improve income and reduce poverty. However, there is limited access to extension services in most parts of the country with the National extension staff: farmer ratio standing at 1 : 1,500. This situation has hindered most farmers from keeping pace with changing technological advances.
SOLUTION: There is therefore need for recruitment of more extension staff and the involvement of NGO’s to increase access of extension services to farmers.
6. Use of obsolete technology
Use of modern science and technology in agricultural production is still limited despite having a well-developed agricultural research system in Kenya. Inadequate research extension farmer linkages to facilitate demand-driven research and increased use of improved technologies continue to constrain efforts to increase agricultural productivity as farmers continue to use out-of-date and ineffective technologies.
SOLUTION: this brings the need of extension services that can link research and the farmers.
7. Deterioration of soil nutrients.
The ever-rising population has contributed to the subdivision of land to uneconomically small units. In addition, the reduction of fallow periods and continuous cultivation has led to rapid depletion of soil nutrients, declining yields and environmental degradation.
SOLUTION: Farmers need information on the proper farming practices such as crop rotation and intercropping, aimed at restoring the soil nutrient.
8. Socio-cultural factors/negative attitude towards agriculture
People tend to develop poor attitude towards agriculture as an occupation with the assumption that agriculture is either dirty or it is energy consuming and prefer those pre-occupation that tend to prepare people for white collar jobs.
9. Poor land tenure system such as land fragmentation and communal land tenure
Poor rainfall and poor government land legislation systems have led to use of land in Kenya difficult, sometimes preserved as game reserves or national parks on high potential land that can be used in agricultural investment.
10. Poor marketing structures
Inefficient transport system makes the farmer incur heavy losses due to spoilage in transit.
11. Poor crop and animal husbandry
There is an increase of poor crop and animal husbandry practices, poor land cultivation and poor storage facilities.
12. Lack of labour
13. Price fluctuations- Due to changes in the supply and demand prices of most agricultural products to change from time to time vigorously.
FUTURE DEVELOPMENT OF AGRICULTURE
1. Technological improvement
Government has continuously encouraged the adoption of new farm technology which is an incentive in improving agricultural productivity.
2. Agricultural education
The government has expanded and stressed agriculture education from primary to university resulting to many agricultural graduates helping farmers to improve in farming techniques.
3. Marketing board
The government has developed effective market e.g boards effective in handling agricultural produce such as C.B.K, N.C.P.B etc
4. Agricultural research
This has led to improved crop and livestock breeding techniques such that waste land has been rehabilitated in order to increase the area of land that is used for agricultural production. It has also led to effective control of pests and diseases as well as developing efficient method of storage and processing in order to minimize farm level.
5. Cooperative societies
The government has encouraged farmers to form cooperative society that can handle marketing of farmers produce besides provision of farm inputs such as fertilisers, farm tools and short term credit facilities to farmers.
6. Land tenure systems
Farmers are encouraged to prefer land adjudication and registration so that they can have tittle deeds to secure loans to improve their farming technology.
7. Transport system
The government has started to improve the transport system especially the road network and therefore it is easy to collect and dispatch farm produce to the market in time. It saves a lot of losses for agricultural produce especially those ones that are highly perishable.
FARMING SYSTEMS
A farm is any tract of land or water consisting of one or more parcels and devoted to the cultivation of plants or rearing of animals under the management of a farmer. Cultivation of acquatic life forms part of this definition because they are raised on a track of water.
A system is a group of defined components which can be further sub-divided and have recurrent interaction. The interactions are assumed to be more frequent than those occurring between components inside the system and it may be open and elastic to change.
In a system, the inputs should be able to lead to multiplied effect such that the output may be more than the inputs produced.
A Farming System is a unit consisting of a group under the management of human effort in an environment and getting involved in the direct production of plants and animal products.
A Farming System is also described as an ecosystem in which all the components of land, labour, capital, cropping systems, animal production systems and farm machinery are considered together to produce goods to meet all the needs of the farmer/ society.
A Farming system is also part of large social, political, economic and cultural environment with an impact to farming. This depends on:-
v Climate and weather.
v Land quality and land tenure.
v Socio-economic variables existing at the time.
TYPES OF FARMING SYSTEMS/METHODS OF FARMING
1. Shifting Cultivation
This is where a piece of land is cleared, farmed for a few years and then abandoned in preference for a new site. While the new site is being farmed, natural vegetation is allowed to grow on the old site. Eventually, after several years of bush fallows, the farmer returns to the original location.
Features of shifting cultivation
i. Selection of a fallow land is common
ii. Clearing of land or bush using hand tools during dry season is common.
iii. Crops are grown on the field for one or two years starting with heavy feeder crops.
Advantages of shifting cultivation
v It has low capital investment.
v Self-sustaining and therefore for simple farmers is convenient if other issues are not important. The self-sustaining depends on:
- Recycling of nutrients
- Fallen leaves add a lot of organic matter and nutrients.
v Forest and/or savannah provide good soil cover.
v Reduced leaching under the fallow.
v Reduced losses due to pests and diseases.
v No land disputes as land ownership is not individualized.
Disadvantages of shifting cultivation
v Difficult to increase productivity of labour and land i.e it is extensive and difficult to intensify thus low productivity.
v A lot of time is wasted when the farmer is shifting and building structures.
v Farmers have no incentives to develop land and conserve water and soil.
v Not applicable in areas of high population density or where there is a high population increase.
v It requires a great deal of land to maintain the system.
It tends to discourage high level of inputs.
2. Mixed Farming
This is a system which involves complete integration of animal husbandry under proper farm management. In this combination, animals provide manure for crops while crop residues are used to feed the animals. Sometimes integration of the production of crops and animal production enterprises can increase the total productivity of some or all holders. This can also improve the welfare of 60% of the people.
Socio-Economic characteristics of Mixed Farming.
v Subsistence – there’s more sale of surplus products in order to raise money to purchase inputs. This system is economically very stable because of effect on the increase of income which is spread evenly over other enterprises.
v Labour requirement can be very high on use in such activities like feeding animals, cutting of forage, transportation.
v It requires considerable management skills in order to ensure the crop and animal activities that are combined are managed properly.
Physical Characteristics of Mixed Farming
v Basic sustainable mixed farming practices are found in high potential areas.
v Farm animals should be close to water sources, since large quantities of water are required and herding would be made very practical.
v Soil quality is also important since it determines biomass production.
v Crop production component include annual stable crops e.g maize, rice, millet etc and and also includes fodder crops e.gnapier grass and lucerne, vegetables, fruit crops e.g mango, tree crops e.g coffee, tea, cashew nuts and cash crops.
v It can combine large variety of components; dairy cattle, beef and multipurpose animals, poultry and fish farming.
Soil Fertility Management
The strength of mixed farming systems lies on its ability to maintain soil fertility in all costs through soil nutritive practices like mulching, manure application and planting with inorganic fertilisers.
3. Arable Farming
This system involves cultivation of land to grow crops, grasses, fodder crops to sustain the animals. This system can be very subsistence where a household produces its crops for food consumption and just a little for sale.
4. Pastoral Farming
This is a system where nomadic people move with their animals from one place to another in search of water and pastures for the animals.In many areas, nomadic pastoralism is on the decline because more land is coming under cultivation e.gMaasai Mara where a lot of land has been converted to wheat farming.
5. Organic Farming
It is a farming system which utilises organic materials as either an external or recycles input to produce crops or subsistence or commercial purposes. The system uses the following types of materials:-
v Fresh dry composite from livestock and poultry.
v Crop residues which are recycled after harvesting the crop.
v Green manure which is obtained on the farm.
v Biomass resulting from short to long term fallowing.
v Agro-industrial by-products e.g coffee husks, filter mud, bagasse.
v Forest litter which can either be leaves, wood, bark materials.
v Coarse (rough) organic material which are applied in the surface in form of mulch.
Role of Organic Farming
a. Physical functions
ü Organic matter binds soil particles together into soil aggregates which leads to good soil structure.
ü Good soil structure has high porosity that leads to easy root penetration.
ü Improvement in gaseous exchange, drainage and water retention capacity.
ü It facilitates the presence of soil micro-organisms that are important in plant and animal decomposition.
ü It assists in the reduction of soil temperature and high soil moisture storage because the soil is properly flocculated.
b. Chemical function
ü Continuous organic input in the soil enhances plant nutritional status especially direct supply of Nitrogen, potassium and phosphorus.
ü It has also been proven that organic nitrogen and sulphur are readily mineralised into organic forms.
ü The incorporation of organic nitrogen and sulphur protects those elements from leaching.
ü The slow release of nitrogen, sulphur and phosphorus through mineralisation is important for sufficient plant availability.
ü Organic inputs enhance Ion exchange capacity.
ü It is very important in plant availability so in sandy soils where aluminium and iron toxicity can easily lead to phosphorus fixation.
c. Biological function
ü Organic farming tends to stimulate the activities of micro-organisms which have a role to play in organic matter which have the ability to act on cellulose micro-nutrients present in plants which eventually constitute the soil biomass.
ü The decomposition process is catalysed in such a manner that nutrients are availed highly.
ü Termites have ability to break cellulose that are present in the soil which eventually constitute soil biomass.
d. Livestock Farming
It is the keeping of animalse.g goats, fish, sheep, pigs, bees for the sake of harvesting products such as meat, eggs, milk, wool, honey, hides & skins.
Generally, there are three practices of livestock farming which are used by farmers in Kenya:-
i. Pastoralism
ii. Commercial farming
iii. Ranching.
e. Rotational cropping system
It is a carefully considered crop sequence that ensures a farmer to grow different crops on the same piece of land without any fallow period in between.
It is also the continuous growing of different crops on the same piece of land in an orderly sequence.It requires operations of long-term value on the land to be carried out, since the land will be used on long-term basis. Such operations include:-
i. The removal of stumps and wood roots from the field. It is a must where mechanical services are used on the land e.g weeding.
ii. Construction of contour bands for soil erosion control.
iii. Grading of land for irrigation purposes.
CROP ECOLOGY
Crop ecology is a sub discipline of ecology which studies the distribution and abundance of plants, the effects of environmental factors upon the abundance of plants and other organisms.
It can also be defined as the study of the relationship existing between crops of different types and how they relate to their environment.
BIOLOGICAL INTERACTIONS IN CROP ECOLOGY
(1) Mutualism – this is an interaction between two species or individuals that is beneficial to both. E.g plants and mycorrhizae fungi. The plant is assisted with nutrient uptake, while the fungus receives carbohydrate.
(2) Commensalism – one plant exploits another e.g epiphytes which grow on branches of tropical trees, or even mosses which grow on trees in deciduous forests.
(3) Herbivory – this is an ecological function of plants where they produce organic compounds for herbivores in the bottom of the food web.
(4) Competition – plants require relatively few basic elements as C, H, N, O, P and S life forms. When plants grow in close proximity, they may deplete supplies of these elements and have a negative impact upon neighbours.
ECOLOGICAL FACTORS
These are environmental factors consisting of conditions that prevail in an area and their influence in crop performance in that particular area. They are classified into two main categories. Namely :-
(i) Biotic factors.
(ii) Abiotic factors.
Abiotic factors
Abiotic factors refer to non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. They include physical conditions and non-living resources that affect living organisms in terms of growth, maintenance and reproduction.
Examples of abiotic factors include:-
Ø Water/Rainfall
It is a precipitation from the sky which is important for soil conditioning and also for plant growth and development. Water is important in plant life processes such as photosynthesis, translocation etc.
Different plants require different amount of water for their survival. Lack of enough water in plants is indicated by wilting. Insufficient water in plants may be as a result of low soil water holding capacity or higher transpiration rate than absorption.
Functions of water to plants
ü It provides hydrogen needed in the manufacture of carbon-hydrogen nee d by plants. 6 CO2 + 12 H2O ------> C6H12O6 + 6 H2O + 6O2
ü It acts as a solvent and transportation medium for plant nutrients.
ü It acts as a medium for chemical reactions.
ü It cools down plants during transpiration.
ü It keeps plant cells turgid. Water content a plant depends on:-
· Species of plants.
· Stage of growth.
· Part of the plant.
Generally, water content of a plant vary between 50% and 90%.
Ø Amount of sunlight.
Ø Wind.
Ø Ambient temperature.
This is a measure degree of coldness or hotness of a given place. It influences the physiological processes of plants e.g photosynthesis, respiration, mineral absorption and food translocation. Most plants grow in a temperature range of 4o C – 36oC. Temperature and altitude are closely related because for every rise in altitude from sea level, there is a drop of 1.7 oC – 2.2 o C temperature.
Ø Humidity.
Ø PH of the water soil in which an organism lives.
Biotic factors
These are factors of biological nature, or arse from living things, that will negatively or positively affect production in agriculture. Those that negatively affect agricultural production include the following:-
Ø Pests. These are destructive organisms which affect agriculture by feeding on the whole or parts of the plant; transmit crop diseases; injure the plant parts which they feed on and as a result expose the plant to secondary infection; and they increase the cost of producing crops.
Ø Parasites. These are invertebrates which live in or on the plants and animals.
Ø Pathogens. These are micro-organisms which transmit diseases.
Ø Predators. A predator is an animal that kills and feeds on another animal. Predators that feed on pests are beneficial to farmers as they reduce pest population.
Those that positively affect agricultural production include the following:-
Ø Decomposers. These are micro-organisms that act on plant and animal materials. They cause rotting of such materials forming manure.
Ø Pollinators. These can be insects or birds which transfer pollen grains from the stamens to the pistil of the flower, causing cross pollination.
Ø Nitrogen fixing bacteria. These are useful micro-organisms in leguminous plants. They convert nitrogen from the air into nitrates.
Biotic components are living things that shape an ecosystem. A biotic factor is any living component that affects another organism, including animals that consume the organism in question, and the living food that the organism consumes. Each biotic factor needs energy to do work and food for proper growth. Biotic factors include human influence. Examples of biotic factors include the availability of food organisms and the presence of competitor, predators and parasites. Biotic components usually include:-
Ø Producersi.e autotrophs such as plants which convert the energy from photosynthesis (the transfer of sunlight, water and carbon dioxide into energy) or other sources into food.
Ø Consumersi.e heterotrophs such as animals, they depend upon producers (occasionally other consumers) for food.
Ø Decomposers i.edetritivores such as fungi and bacteria, they break down chemicals from producers and consumers (usually dead) into simpler form which can be reused.
FACTORS LIMITING CROP PRODUCTION
EXTERNAL FACTORS
CLIMATIC FACTORS
Climatic factors have the highest influence on crop production, some of the main factors include;-
i. Rainfall.
Rain is the source of water necessary for all life processes. Lack of rain means that farmers cannot plant new crops and the growing ones may wilt and die or they may not yield as expected. Therefore rainfall must fulfil the following conditions for good growth:-
ü It must be enough to meet the requirements of the crop.
ü It should be well distributed during the growing period of the crop.
ü It must be reliable in terms of quality and timing.
ü It should have the right intensity.
ii. Temperature.
Temperature is closely related to altitude, because the higher the altitude the lower the temperatures. Temperature affects crop production in the following ways:-
ü Crop distribution – most crops does well between 4.5*c and 36.0*c. however, each crop has its own optimum range of temperature. This gives rise to different crops being cultivated in different areas.
ü Temperature affects disease incidence in crops. For example, at high altitudes coffee diseases such as CBD and Elgon dieback are common whereas at low altitude rust disease in coffee is a problem.
ü Temperatures affect the rate of biochemical reactions. For example, the sweetness of pineapples and the higher acid content of fruits increase by increase in temperature. On the other hand, pyrethrum quality increases with rise in altitude.
iii. Light.
Light is needed for photosynthesis and without it plants will not be able to produce food. Plants grown in the dark have elongated yellow leaves. There are three aspects of light that are important to crop production:-
ü Light intensity – this is the brightness of light, high intensities also mean high temperatures this increases transpiration and may cause wilting.
ü Light duration or day length – this refers to the period during which light is available for use by plants. Some crop plants flower in response to the length of the day such as rice, maize and sorghum.
ü Light wavelength – this makes natural rather than artificial light more suitable for plant growth. Chlorophyll absorbs certain wavelengths of light which are not present in artificial light unless in case of ultra-violet or infra-red
iv. Wind.
Wind affects crop production in the followingways:-
ü Helps in pollination of most cereal crops.
ü Increases the rate of evaporation from plants, thereby increasing the rate of water uptake by plants. On the other hand, wind :
ü Spreads some crop diseases such as rust in wheat.
ü Increases loss of water through evapotranspiration, causing wilting where there is water stress.
ü Causes lodging or blowing over of crops.
ü Cause distortion in perennial crops.
ü Cause soil erosion if very strong.
SOIL FACTORS
Soil is defined as the natural material on the earth’s crust in which the roots of plants grow. Soil can also be defined as the loose natural material on the earth’s crust formed from weathered materials on which plants grow and get water, nutrients and anchorage through the roots. It affects crop production in the following ways:
a. Fertility – soil is the medium from which plants get their nutrients and water.
b. Soil texture – this will determine water holding capacity and drainage, hence affecting crop growth. It determines the method of irrigation that is suitable. This is crucial in the growing of crops like paddy rice which require flooding such as clay soil.
c. Soil acidity or alkalinity will to some extent determine what crops can be grown well in a certain area. For instance, tea will require acid soil. At the same time PH affects the availability of some nutrients.
PLANT FACTORS
i. Cultivars or clones
A cultivar is an assemblage of plants that has been selected for a particular character or combination of characters; it’s distinct, uniform and stable in those characters and when propagated by appropriate means, retains those characters. It’s a plant or group of plants selected for desirable characteristics that can be maintained by propagation.
ii. Type of seed/dormancy
This is where some seeds undergo a period of dormancy ( the stage where a seed cannot germinate)between their maturity and the time they sprout. Therefore this period should be broken before the seed is planted. Methods of breaking seed dormancy are as follows:-
a. Soaking in water. Seeds are soaked in water for a period of between 24 – 48 hours until they swell i.e the seed coat is softened.
b. Chemical treatment. Seeds are dipped in specific chemicals like concentrated sulphuric acid for two minutes and then removed.
c. Mechanical method or scarification. The outer coat is scratched to make it permeable to water.
d. Heat treatment. The seeds are soaked in hot water of about 800*c for 3 – 5 minutes after which water is allowed to drain off.
SOCIAL ECONOMIC FACTORS
a. Capital
Every farmer requires capital to invest in the development of his farm. Mostly farmers obtain their capital as loans, but those without security cannot access loans and many of them are small scale farmers who usually produce for subsistence use, making the level of investment in their farms to be low.
b. Attitude
For a long time, people in the developing countries, have tended to have a poor attitude towards agriculture as an occupation. Most of the bright man- power migrates to urban centres in search of white collar jobs leaving behind the old and the less well-educated to tend the land.
c. Infrastructure
Sometimes the transport system is inefficient or unavailable thereby leading to spoilage of produce due to the delay in delivering it to the market.
d. Taboos
Some cultural and religious beliefs of a given society affect the type of crops to be grown in an area. This would also affect the systems and methods of farming.
e. Markets
This directly affects the production of farm produce. Ready markets for agricultural produce should be reachable by farmers to avoid spoilage of their produce. Market forces (demand and supply) also affect production because producers can only supply what the market is willing to buy at a certain price and time.
LAND PREPARATION
Land preparation refers to the initial activities that are carried on land to make it suitable for crop production. A seedbed is a piece of land varying in size from a few square metres to hundreds and even thousands of hectares, that has been prepared in such a way that it is ready to receive the seed or planting material. For the land to be ready for planting, the condition of the soil, for example the size of the soil clods, depth of soil and the looseness of the soil must facilitate planting, germination of the seed and subsequent growth of the plants. Land preparation operations include activities such as:-
- Ploughing or digging.
- Harrowing. - Rolling.
REASONS FOR SEEDBED PREPARATION
1. To kill weeds either by burying them or by desiccation through exposure to the sun.
2. To bury crop residues from the previous season’s crop so as to make it easy to plant.
3. Seedbed preparation operations loosen up the soil thereby facilitating rainfall infiltration into the soil as well as improving soil aeration.
4. Seedbed preparation may be aimed at breaking hard soil surface that may sometimes form with the result that rainfall acceptance of the soil is impeded.
5. It encourages the penetration of roots in the soil.
6. It aerates the soil.
7. It destroys crop pests in whichever stage by burying them or exposing them to the heat of the sun and predators.
8. It makes farm operations such as planting, fertiliser application, rolling an ridging possible.
TYPES OF SEEDBED PREPARATION
· Clearing.
· Primary cultivation.
· Secondary cultivation.
· Tertiary cultivation.
· Minimum tillage.
CLEARING
This involves the clearing of land by removing all the vegetation from its surface.
Clearing of land is necessary under the following conditions:
ü When opening up virgin land.
ü Where a stalk growing crop was previously planted.
ü Where the interval between primary and secondary cultivation is long such that land has reverted to the original virgin state.
ü Where land was left fallow for a long time.
The following activities are undertaken when clearing land:-
Ø Tree felling: this involves cutting down or uprooting forest trees using axes, pangas, small power saws and bulldozers.
Ø Burning: fire is introduced to burn the vegetative cover and clear the land. However, the use of fire comes with disadvantages such as fire spreading to other fields, destruction of organic matter, soil micro-organisms and plant nutrients.
Ø Slashing: small bushes and grasses are cleared using a panga or a tractor-drawn mower.
Ø Use of chemicals: chemicals (herbicides) are used to kill weeds.
PRIMARY CULTIVATION
This is the practice of opening up land by using jembes in small-scale farming and ploughing using tractors in large-scale farming. Primary operations include such activities as initial opening up of the land through ploughing. Primary operations are a heavier job and therefore employ heavier implements as well as being more time consuming and costly.
Reasons for primary cultivation
Ø Making planting easier.
Ø Removal of weeds.
Ø Burying organic matter into the soil for easy decomposition.
Ø Improving water infiltration and aeration of the soil.
Ø Destroying soil-borne pests by exposing them to predators.
Primary cultivation can be achieved through any of the following ways:
Ø Hand digging.
Ø Mechanical cultivation using tractor-mounted implements which include mouldboard and disc ploughs.
Ø Use of an ox-plough.
SECONDARY CULTIVATION.
Secondary operations follow the primary operations and include mainly harrowing. These operations are less onerous and the rate of work is comparatively faster than for primary operations.
Factors to determine the number of secondary cultivations
(a) The condition of the land i.e a fairly weed-free land will only need a minimum number of cultivations to produce a good seedbed. While a bushy piece of land with much trash to bury will require more cultivations before the seedbed is ready for planting.
(b) The type of seed or planting material to be used. A seedbed for planting a crop having very tiny seeds such as wheat, barley or millet will need to be reasonably fine for best results. In contrast, a seedbed for planting sweet potato vines, or irish potatoes need not be as fine since the planting materials in this case are much larger and can cope with a roughish seedbed.
(c) Type of soil i.e most tropical soils lose their structure if they are over-cultivated both during seedbed preparation and in subsequent weeding of the crops.
(d) Slope of the land.
(e) Time available before planting.
(f) Moisture content of the soil.
(g) Skills of the operator.
Importance of secondary cultivation
Ø To break the soil clods into small pieces for easy planting.
Ø To level the field in order to achieve a uniform depth of planting.
Ø To incorporate organic matter into the soil in order to encourage decomposing before planting.
Ø To remove any weeds that might have germinated immediately after primary cultivation.
TERTIARY OPERATIONS
These are special operations carried out to suit certain crops. They are normally carried out after primary and secondary cultivation. They include:-
Ø Levelling. This is the practice of making the soil surface flat and uniform so as to facilitate even germination of small seeds.
Ø Rolling. Heavy rollers used to compact the soil before planting small seeds.
Ø Ridging .this is a process of digging soil in a continuous line and keeping it. It is important in growing Irish potatoes, sweet potatoes, cassava and groundnuts.
SUB-SOILING
This is the process of breaking hardpans which form as a result of cultivation at the same depth for a number of years. Chisel plough, cultivators and sub-soilers are used for this purpose.
Importance of Sub-soiling
Ø It breaks up the hardpans in areas where they have formed after land preparation.
Ø It also helps in facilitating adequate gaseous exchange in the soil and bringing to the surface minerals which might have leached to the deeper layers.
MINIMUM TILLAGE
This involves use of at least number of cultivation operations either during the preparation of the seedbed or during the management of subsequent crops.
It is also a term used to describe the application of a combination of tillage practicesaimed at minimum disturbance of the soil while maintaining optimum physical conditions required for proper crops growth. For instance, minimum tillage practices involve:-
Ø Spraying herbicides.
Ø Establishing a cover crop on the field.
Ø Uprooting.
Ø Slashing weeds in perennial crops such as coffee.
Reasons for minimum tillage
Ø To control or minimise soil erosion.
Ø To reduce the cost of cultivation or ploughing.
Ø To maintain soil.
Ø To conserve moisture.
Ø To prevent disturbance of roots and underground structures.
Ø To prevent exposure of humus to reduce volatilisation of nitrogen.
METHODS OF PREPARING SEEDBEDS
Hand method
This involves the use of a wide range of hand tools such as pangas, and jembes. The pangas may be used for clearing the bush or for weeding the crop.
Preparation of a seedbed by hand is a slow process, thusonly a few hectares are capable of being managed by this method.
Because of their nature, hand tools, such as the jembe are not suited to digging if the soil conditions are very hard, for example, during the dry season. This means that the farmer must wait until after the first rain showers have wetted and softened the ground before he can commence digging. Hence seedbed preparation tends to be late, especially if the hectares involved is large and the soil is the type that tends to become extremely hard in the dry season. Because of lateness in seedbed preparation, planting is also late, often leading to poor crop yields.
Hand-prepared seedbed tends also to be limited in depth as the tools employed are not designed to penetrate very deeply.
Some soils may be too compacted to prepare by hand.
Mechanical seedbed preparation
Mechanical seedbed preparation involves mainly the use of tractor-mounted or trailed implements such as various types of ploughs, harrows and cultivators. The use of machinery is costly and therefore it is largely confined to the large scale farms such as coffee, sugar and tea estates, wheat growing farms. Otherwise small scale farmers who may be owning only a few hectares of land can profitably hire machinery from contractors to do the ploughing or the harrowing for them.
In some special cases small scale farmers can afford operating tractors and the ancillary implements if the farming enterprise they are engaged in is intensive and highly profitable. Thus some farmers growing horticultural crops such as vegetables, fruits and flowers, mainly for exporting, can afford the use of machinery even on small holdings of as few as ten hectares or less.
For the most efficient use of machinery in seedbed preparations, the timing of the operations, the choice of the correct implement for the specific job and the correct setting of the implements during its operation are very important. Thus very wet soils should never be worked with ploughs or harrows otherwise the soil structure may be destroyed by paddling. Similarly very dry soils may be difficult to penetrate with the ploughs. It is therefore imperative to time the tillage operations to coincide with the time when the soil moisture is at its optimum for working. Usually the time immediately following harvesting of a crop such as wheat, or maize is the best one to plough up the land as there is yet some moisture left in the soil to facilitate ploughing.
Advantages of mechanical land preparation
Ø Quick rate of work i.e large area is capable of being prepared in minimum time.
Ø Better burying of the weeds.
Ø Machinery can efficiently cope with difficult soil conditions.
Ø Less laborious. Human labour is spared to do the necessary planning of the farm operations.
Ø Land preparation is done on time and therefore planting is done at the correct time and therefore planting is done at the correct time leading to high yields.
Disadvantages of mechanical land preparation
Ø Machinery is costly.
Ø Skill is needed to operate the machinery efficiently.
Ø Maintenance of the machinery is costly.
TIMING OF OPERATIONS
Reasons for timely operations
Ø It allows ample time for the land to weather and for the weeds.
Ø It ensures early planting.
PLANT PROPAGATION
DEFINITION
Plant propagation involves the formation and development of new individuals which are utilised in the establishment of new plantings.
Life cycles of plants
i) Annual crops.
ii) Biennial crops.
iii) Perennial crops.
Stratification is the process of treating stored or collected seed prior to sowing to stimulate natural winter conditions that a seed must endure before germination. Stratification is the process of subjecting seeds to both cold and moist conditions. To accomplish this you merely place the seeds in a sealed plastic bag with moistened vermiculite(or sand or even a moistened paper towel) and refrigerate it. It is important to only slightly dampen the vermiculite, as excessive moisture can cause the seeds to grow mouldy in the bag.
After undergoing the recommended period of stratification, the seeds are ready to be removed and sown in the nursery bed for germination. Alternatively, the seed may be sown in small pots filled with moist soil and then the whole thing enclosed inside a plastic bag before placing inside a common refrigerator.
Preparing a stratifying medium
The seeds should be cleaned of any additional material (fruit pulp, leaf seed-pod fragments, cones scales etc) but the shells of nuts should not be removed.
Many sources recommend using peat, a combination of peat and sand, or vermiculite as the medium for cold stratifying seeds. The medium must be sterile to prevent harm to the seed by pathogens including fungi.
Soaking the seeds in cold water for 6-12 hours immediately before placing them in cold stratification can cut down on the amount of time needed for stratification, as the seed needs to absorb some moisture to enable the chemical changes that take place.
Any seeds that are indicated as needing a period of warm stratification should be subjected to the same measures, but the seeds should additionally be stratified in a warm area first, followed by the cold period in a refrigerator later. Warm stratification requires temperatures of 15-20oC(59-68oF). In many instances, warm stratification followed by cold stratification requirements can also be met by planting the seeds in summer in a mulched bed for expected germination the following spring. Some seeds may not germinate until the second spring.
Use of fungicide.
Use of a fungicide to moisten your stratifying vermiculite will help prevent fungal diseases. Different seeds should be placed in different bags rather than putting them all into one bag, and large quantities are also best split into several small bags. That way any fungal outbreak will be restricted to only some seeds. If no fungicide is used, a close check should be kept on the seeds, removing any which show signs of mould or become soft and with a decaying smell.
If an outbreak of fungus occurs, remove the seeds and re-apply fungicide, then place them in a new bag with new slightly moistened vermiculite. Always keep the bag sealed. The stratifying seeds should be checked on a regular basis for either fungus or germination. If any seeds germinate while in the refrigerator, they should be removed and sown.
Sowing and seedlings
Most seedlings, whether grown in pots or beds, benefit from good air circulation which discourages fungus growth and promotes sturdy stems.
Potting and germinating medium/soil is not critical as long as the soil is light as well as lightly firmed down but not heavily compacted. Sterilised potting soil will minimizes problems with Botrytis or Pythium fungal disease. These problems are much more likely to occur
Most seeds need only be planted at a depth equal to their own thickness in order to germinate. Seeds planted outdoors are best planted little deeper to avoid disturbance caused by heavy rainfall. The soil should be slightly damp but never soaking wet, nor allowed to dry out completely.
Reasons for plant propagation
· It perpetuates plants as independent units.
· It ensures that plants are not lost to man by reverting to less desirable forms.
· Through selection and propagation of only certain varieties with desirable characters, man has built up a wide range of crop plants of great economic importance from naturally existing species but of diverse characteristics.
Methods of plant propagation.
(1) Propagation by seed (sexual propagation).
(2) Vegetative propagation (asexual propagation).
PROPAGATION BY SEED.
Reasons why seeds are used include:-
Ø Seeds are easy to treat against pests and diseases.
Ø Seeds are not bulky and therefore storage is easy.
Ø Seeds are easy to handle during planting making the operation faster.
Ø Fertiliser and manure application can be mechanised.
Ø It is possible to develop new crop varieties due to crosspollination.
Ø When planting seeds, it is easy to use machines like seed planters and drillers.
Disadvantages of using seeds as planting materials
Ø Some seeds have long dormancy and may need special treatment in order to germinate.
Ø Plants raised from seeds have variations from the mother plant due to cross pollination. This may introduce undesirable characteristics.
Ø Soil borne pests may damage seeds if left for sometimes in the soil before rain falls.
Ø Some seeds may lose viability if stored for a long time.
VEGETATIVE PROPAGATION.
The method relies on the use of vegetative structures such as stems, leaves or roots to perpetuate the parent plants. The vegetative parts contain or develop buds which give rise to new individuals.
Advantages of using vegetative materials for planting.
I) Crop originating from vegetative materials mature faster than those from seeds.
II) The crops show uniformity in such qualities as disease resistance, seed size, colour, keeping or storing quality and chemical composition.
III) It is possible to produce many varieties of compatible crops on the same root stock.
IV) Use of the vegetative materials is easier and faster, especially where seeds show prolonged dormancy.
V) The resulting plant has desirable shape and size for ease of harvesting and spraying.
VI) It facilitates the propagation of crops which are seedless or those that produce seeds which are not viable or have long dormancy.
Disadvantages.
i) Vegetative propagation does not result in new crop varieties.
ii) Keeping the materials free of disease is difficult.
iii) Materials cannot be stored for long.
iv) The materials are bulky and therefore difficult to store and transport.
Plant parts used for vegetative propagation
(i)Bulbils.
These are tiny sisal plants produced in the inflorescence almost at the end of the plant growth cycle.
(ii) Splits.
These are plantlets divided from the existing mother plant with complete leaves and rooting system.
(iii) Crowns and slips.
These are materials used to propagate pineapples. Crowns are born on top of the fruits and are broken off and prepared for planting. Slips are born at the base of the pineapple fruit, they take 22 months from planting to maturity.
Crowns and slips are planted in the nurseries first before transplanting to the main seedbed.
(iv) Suckers.
These are small plants that grow from the base of the main stem. They have adventitious roots which grow quickly when planted to form a new plant.
(v) Tubers (stem and root tubers)
These are underground structures or food organs which are short and thick. They sprout and produce roots for growth.
(vi) Vines.
These are soft wood cuttings which produce roots easily upon planting to give rise to new plants. They are cut from the mother plants and planted directly into the field.
(vii) Cuttings and setts.
Cuttings are portions of plant parts which are cut and then planted. They may be from stems, roots or leaves. A stem cutting must have a bud which develops into a shoot. The root cutting must have an eye.
LAYERING
Layering is the process used to induce a part of a plant to produce roots while it is still attached to the mother plant.
Types of layering
(i)Marcotting / Aerial layering
This is aerial layering commonly used on plants with stems that cannot bend easily. Some moist rooting medium is heaped around a section of the branch whose bark and cambial layer have been removed. The rooting medium is then wrapped with a polythene sheet to hold the soil and maintain the soil moisture.
At the point where the bark has been removed, auxins accumulate and thereafter induce development of roots. The rooting medium quickens the process of rooting.
(ii) Tip layering
In this method:
- The shoot bearing the terminal bud is bent into the ground and covered with a layer of moist soil.
- It is held in position by use of pegs.
- The covered part of the shoot is induced to produce roots after which it is cut off from the mother plant and transplanted.
GRAFTING
It is a practice of uniting two separate woody stems. The upper part of the union is the scion and the lower part is the stock. The scion must have one or more buds that grow into the fruiting part of the new plant. The scion and the stock are joined together so that the cambium tissues touch and fuse together. Grafting is usually done between two closely related plants like the orange and the lemon.
Grafting methods include:
i) Whip grafting or splice grafting.
ii) Wedge or cleft grafting.
iii) Side grafting.
iv) Bark grafting.
v) Notch grafting.
vi) Approach grafting.
BUDDING
This is a process of propagation where a vegetative bud (scion) is united to the seedling of another plant (root stock). The scion has only one bud and some bark with or without wood. The bud is inserted in a slit made on the bark of the stock. It is held tightly on the stock by tying it with budding tape until it produces a shoot. The wrapping is removed about two weeks after budding in order to inspect the buds. If they are green they are accepted by the root stock. The stock is then cut a few centimetres above the union. The green bud develops to produce a shoot.
Methods of budding include:
i) T- budding.
ii) Patch budding.
iii) Top budding.
Importance of budding and grafting
i) Plants with desirable root characteristics such as disease resistance, vigorous root system, and resistance to nematode attack but with undesirable products may be utilized to produce desirable products e.g lemon-orange graft.
ii) They make it possible to grow more than one type of fruit or flower on the same plant.
iii) They help to propagate clones that cannot be propagated in any other way.
iv) They help to shorten the maturity age. Grafted mangoes. For example, may take three and half years to mature while non-grafted mangoes may take up to seven years to mature.
v) They facilitate the changing of the top of the tree from being undesirable to desirable.
vi) Grafting helps to repair damaged trees.
TISSUE CULTURE (BIOTECHNOLOGY)
Tissue culturing is a biotechnology which is being used extensively in cloning of vegetatively propagated plants. It is based on the ability of plant tissues (cells) to regenerate other parts of the plants. Tissues which are also called propagules or explants, are derived from shoot tips where cells are undergoing rapid cell division and are not differentiated. The cells are then provided with the right conditions which enable them to multiply and develop roots and shoots.
These conditions include a culture medium which contains the correct nutrients and growth regulator. They are also subjected to the correct light intensity, temperatures and relative humidity.
Propagation of plants by tissue culture follows a sequence of stages:
Stage 1: The initial phase.
It involves establishing the aseptic culture and developing the propagule by enhancing cell division and enlargement. Contamination is eliminated by using disinfectants such as:
- Alcohol.
- Calcium or sodium hypochlorite.
- Mercury chloride.
- Antibiotics.
All tools used must be sterilised to establish a clean culture. The ingredients of the culture medium at this stage include:
- Inorganic minerals.
- Carbon.
- Energy source- sugar.
- Vitamins.
- Organic supplements.
- Growth regulators.
Stage 2: The multiplication phase
It involves a series of sub-culturing to rapidly multiply the propagules through somatic development of embryos to produce auxillary buds and adventitious roots. The culture medium at this stage should be enriched with substances/ growth regulators that enhance the development of plant organs as well as inducing the proliferation of multiple shoots. Growth regulators include: Auxins, Abscisic acid, Cytokinins, Ethylene and Gibberellins.
Stage 3:Root formation phase.
It involves the preparation of the propagule for the establishment in the soil. This propagation includes the following:
i) Rooting of the regenerated plantlets.
ii) Hardening the plantlets by imparting some tolerance to moisture stress and attack by pathogens.
iii) Converting the plantlets from heterotrophic mode of nutrition to autotrophic state. Rooting of the plantlets is promoted by either leaving out the growth hormone in the medium or supplementing the medium with auxins. Hardening occurs due to a change in the physical environments for example, increasing the temperatures and light intensity beyond those in the second stage and gradually exposing the plantlets to conditions similar to those in the field.
IMPORTANCE OF TISSUE CULTURE
Plant tissue culture technology has proven itself to be an effective and viable option for growers to seriously consider in a variety of different situations:
i. It is used to recover and establish pathogen-free plants especially in the control of viral diseases.
ii. It is used in the mass production of propagules.
iii. It is fast and requires less space than the cultural methods of using cuttings which require a bigger space.
iv. When large-scale propagation of new or superior plant varieties is required for early introduction to market. Tissue culture is often the fastest and most economical means to achieve this goal.
v. It is used for mass multiplication for varieties which are difficult to regenerate by conventional methods of propagation.
Tissue culture propagules exhibit the following characteristics:
v Guaranteed to be disease-free.
v Have a more fibrous, healthier root system free of any root rot problems.
v Exhibit a denser, bushier branching habit.
v Characterised by more vigorous growth after transplanting.
v Have a higher survival rate.
v They are ready for re-sale in a shorter time.
LIMITATIONS
i. The method requires highly skilled manpower.
ii. It needs special structures to raise propagules.
iii. It is highly laborious.
iv. It needs specialized culture medium which is expensive.
PLANTING
Planting is the placement of the planting material in the soil for the purpose of regeneration in order to produce more of the plant species.
SELECTION MATERIALS
Factors considered when selecting planting materials:
ü Suitability to the ecological conditions. The selected planting materials should be well adapted to the soil conditions, temperatures and the amount of rainfall in the area.
ü Purity of the materials.Planting materials should be pure and not mixed with other off-types.
ü Germination percentage.This is a measure of the germination potential of seeds.
ü Certified seeds. These are seeds which have been tested and proven to have 100% germination potential and free from diseases and pests.
TIME OF PLANTING
The timing of planting or sowing is influenced by the type of the crop to be planted and the environmental conditions of the area.
Factors to consider in timely planting
ü The rainfall pattern or moisture condition of the soil.
ü Type of crop to be planted.
ü Soil type.
ü Market demand.
ü Prevalence of pests and diseases.
ü Weed control.
Timely planting is necessary and should be done at the onset of rains. In some areas where rainfall is scarce dry planting is recommended.
Advantages of timely planting
i. Crops make maximum use of rainfall and suitable soil temperature, leading to vigorous growth.
ii. Crops usually escape serious pest and disease attack.
iii. Crops benefit from nitrogen flush which is available at the beginning of the rain.
iv. For horticultural crops, proper timing ensures that the produce is marketed when prices are high.
v. Crops establish earlier than the weeds, hence smothering them.
Depth of planting
This is the distance from the soil surface to where the seed is placed. The correct depth of planting is determined by:
i. Soil type: seeds will emerge from greater depths in sandy soils that are light than in clay soils.
ii. Soil moisture content: it is recommended that one plants deep in dry soils in order to place the seed in a zone with moist soil.
iii. Size of the seed: larger seeds are planted deeper in the soil because they have enough food reserves to make them shoot and emerge through the soil to the surface.
iv. Type of the germination: seeds with epigeal type of germination such as beans should be planted shallower than those with hypogeal type of germination such as maize.
Spacing and seed rate
Spacing is the distance of plants between and within the rows. Spacing determines plant population and the main aim of correct spacing is to obtain maximum number of plants per unit area which will make maximum use of the environmental factors. Wider spacing leads to a reduced plant population which means lower yields, whereas closer spacing could lead to overcrowding of plants and competition for nutrients and other resources would occur. Correctly spaced crops produce yield of high quality that are acceptable in the market.
Factors that determine the spacing of the crop
i. The type of machinery to be used. The space between the rows should allow free passage of the machinery which can be used in the field.
ii. The size of the plant. Tall crop varieties require wider spacing while short varieties require closer spacing.
iii. Soil fertility. A fertile soil can support high plant population. Therefore closer spacing is possible.
iv. Moisture availability. Areas with higher rainfall are capable of supporting a large number of plants hence closer spacing than areas of low rainfall.
v. Use of the crop. Crop grown for the supply of forage or silage material is planted at a closer spacing than areas of low rainfall.
vi. Pest and disease control. When crops are properly spaced, pests might find it difficult to move from one place to the other, for example, aphids in groundnuts.
vii. Growth habit of the crop. Spreading and tillering crop varieties require wider spacing than erect type.
Seed rate
Seed rate is the amount of seeds to be planted in a given unit area governed by the ultimate crop stand which is desired. The objective of correct spacing of crop is to obtain the maximum yields from a unit area without sacrificing quality. Seeds with low germination percentage are planted at higher seed rates than those which have about 100% germination percentage.
Factors to consider in choosing seed rates.
i. Seed purity.
When planting seed which is pure or with a high germination percentage, less seed is required. On the contrary, more seeds are required when using impure or mixed seed.
ii. Germination percentage.
Less seed is used when its germination percentage is higher. Seed of lower germination percentage is required in larger amounts.
iii. Spacing.
At closer spacing, more seeds are used than at wider spacing.
iv. Number of seeds per hole.
When two or more seeds are planted per hole, higher seed rate is required than when only one seed is planted per hole.
v. The purpose of the crop.
A crop to be used for silage making is spaced more closely than one meant for grain production.
METHODS OF PLANTING
There are practically six methods of planting, namely:
i. Direct seeding and transplanting.
ii. Row planting.
This is where the seeds or other planting materials are placed in holes, drills or furrows in rows.
Advantages of row planting
ü Machines can be used easily between the rows.
ü It is easy to establish the correct plant population.
ü Lower seed rate is used than if broadcasting is adopted.
ü It is easy to carry out cultural practices such as weeding, spraying and harvesting.
Disadvantages of row planting
ü It does not provide an ample foliage cover.
ü It is more expensive than broadcasting because of consuming a lot of labour and time.
ü It requires some skill in measuring the distances between and within the rows.
iii. Broadcasting.
This method involves scattering the seeds all over the field in a random manner. It is commonly adapted for light tiny seeds such as those of pasture grasses.
Advantages of broadcasting.
ü It is easier, quicker and cheaper than row planting.
ü It gives a good ground cover.
Disadvantages
ü It uses more seed than row planting.
ü The seeds are spread unevenly leading to crowding of plants in some places.
ü It results to poor performance due to competition.
ü Weeding cannot be mechanised.
iv. Over-sowing.
This is the introduction of a pasture legume such as desmodium in an existing grass pasture. Some form of growth suppression of existing grass such as burning, slashing or hard grazing plus slight soil disturbance is recommended before over-sowing.
A heavy dose of single superphosphate at the rate of 200-400 kg/ha is applied.
The grass must be kept short until the legume is fully established.
Regardless of the method of establishment, the pasture and fodder stands should be ready for light grazing 4-5 months after planting if rainfall and soil fertility are not limiting.
v. Under-sowing.
This refers to the establishment of pasture under a cover crop, usually maize.
Maize is planted as recommended and weeded 2-3 weeks after the onset of rains.
Pasture seeds are then broadcasted with half the recommended basal fertiliser.
No further weeding should be done and maize should be harvested early to expose the young pasture seedlings to sunlight.
MANURES AND FERTILIZERS
Manures are organic substances that are added to the soil to provide one or more plant nutrients. They are derived from plant and animal remains. Organic manure supplies organic matter to the soil which after decomposition releases plant nutrients.
Fertilizers are chemically made compounds processed for commercial use. They are artificially processed compounds which are added into the soil to improve its fertility. They contain one or more macro-nutrients.
Types of Organic Manure
Manure is classified according to the method of preparation and the materials from which it is made. There are three types of organic manure based on the above classification.
i. Green manure
ii. Farmyard manure
iii. Compost manure
GREEN MANURE
This is a type of manure made of green plants. Plants are grown for the purpose of incorporating into the soil thus improving soil fertility. Examples of plants used as green manure include:
Maize, Sorghum, Sun-flower, Groundnuts, Cowpeas, Sun-hemp, Clovers, Lucerne and Beans.
Characteristics of plants used as Green Manure
ü They should be highly vegetative or leafy.
ü They should have a fast growth rate.
ü They should have high nitrogen content.
ü The plants must be capable of rotting quickly.
ü The plants should be hardy, that is, they should be capable of growing in poor conditions.
Reasons why Green Manure is not commonly used.
ü Most of the crops grown are food crops and it is hard for people to use them as green manure.
ü Green manure crops might use most of the soil moisture and leave very little for the next crop.
ü Most of the nutrients are used up by micro-organisms in the process of decomposing the green manure plant. These will only be released by micro-organisms when they die. They release nutrients to the soil slowly.
ü It takes time for the green manure crop to decompose and therefore planting is delayed.
Preparation of Green Manure
· The crop is planted in the field.
· It is then allowed to grow up to the flowering stage, after which it is incorporated into the soil through ploughing.
· It is then allowed to decompose.
· After this the field should be prepared for planting the major crop.
FARMYARD MANURE (FYM)
Farmyard manure is a mixture of animal waste (urine and dung) and crop residues used as animal beddings in animal houses. The mixture should be allowed enough time to decompose.
Factors determining the quality of FYM
i. The type of animals used. Dung from fattening animals has a higher level of nutrients than that from dairy animals. Non-ruminants such as pigs and poultry absorb less nutrients from their feed and therefore give dung which has a higher level of nutrients.
ii. Type of food eaten feedstuffs that are highly nutritious result in manure with a higher level of nutrients.
iii. Type of litter used. Wood shavings and sawdust are slow to decompose and contain very little nutrients. Farmers are advised to use litter with a high urine absorption capacity.
iv. Method of storage. FYM must be stored well preferably in a place with a leak-free roof and a concrete floor. This is to prevent loss of nutrients through leaching and vaporisation by the action of rain and heat respectively.
Preparation of FYM
· A layer of grass, wood shavings or saw dust is provided in the houses of farm animals to serve as beddings.
· Animals deposit their droppings and urine on the beddings and mix them through trampling.
· After some time, which varies from one type of animal to another, the bedding is replaced.
· The discarded bedding is deposited in a specially prepared shed and new layers of used beddings are continually added until a heap is formed.
· In the course of time, decomposition and mineralisation of these materials take place through the activities of certain bacteria resulting in rich manure. It can then be used in the farm.
COMPOST MANURE
This is a type of manure that is prepared from composed (heaped) organic materials. The compost materials include plant residue and animal waste or plant materials only. Kitchen refuse and left overs may also be included. Materials that should be avoided include synthetics and plants with pests, diseases and weed seeds.
Site selection for making of compost manure
Factors considered:
i. A well-drained place. This avoids waterlogging which leaches nutrients from the manure.
ii. Direction of the prevailing wind. Should avoid direct drift from the compost manure to the dwelling place. This prevents bad odour being blown to the homestead.
iii. Size of the farm. The site should be centrally placed to the area of the farm when compost manure is to be used.
iv. Accessibility. The site must be easily accessible to make it easy for transportation of materials needed.
Preparation of Compost Manure
There are basically two methods of preparing compost manure. These are:
i. Indore Method (Pit Method)
ii. Four heap system (Stack Method)
INDORE METHOD (PIT METHOD)
· The materials to be made into compost are packed into a pit 1.2 m long, 1.2m wide and 1.2m deep. These are placed in layers, starting with fibrous material such as maize stalks which form the foundation of the compost layers.
· This is then followed by a layer of grass, leaves or any type of refuse material.
· On top of this, a layer of well-rotted manure is added to provide nutrients to the micro-organisms.
· This should be followed by a thin layer of wood ash to improve the level of phosphorus and potassium in resulting manure.
· Then a layer of topsoil is added which introduces micro-organisms necessary for the decomposition of the organic materials.
· The above sequence of layers is repeated until the pit is full.
· A layer of soil is added to cover the pit. The pits should be covered to prevent entry of too much water causing waterlogging.
N/B: During the dry season the material should be kept moist by adding water. The vegetative materials used should be young. However, if old crop residues are used, nitrogenous fertilisers should be added to raise the level of nitrogen in the manure.
Diagram:
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Five pits are dug in series and materials filled as follows:
Pits I, II, III and IV are filled with fresh materials as described above. After three to four weeks, the materials in pit IV are transferred to pit V, the materials in pit III to pit IV, in pit II to pit III and in pit I to II. This process is repeated until the material that was prepared first is well rotten and taken to the field as compost manure.
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Pit I |
Pit II |
Pit III |
Pit IV |
Pit V |
Indore method of making compost manure.
iii. FOUR HEAP SYSTEM (STACK METHOD)
In this method, four heaps are used. The materials on each heap are crop residue, animal waste, old farmyard or compost manure, inorganic fertilisers and topsoil.
Preparation
· Surface vegetation and topsoil are scraped off the selected site and then the ground is levelled.
· Posts are fixed at a distance of 1.2 m apart to form the corners of the heap. The posts should be 2m high.
· Wood planks are fixed on the sides and materials arranged as in Indore method.
· If four heaps are used, materials are placed in the heaps labelled X. after three to four weeks, the decomposing materials are transferred to heap Y. after another three to four weeks, the compost materials are transferred to heap Z. it stays for another three to four weeks and is then taken to the field as compost. The manure heaps must be turned occasionally, at least every three months, to facilitate circulation of air within the heap for proper decomposition. The manure is ready for use after six months.
Diagram:
· Top soil.
· Ash.
· Manure.
· Grass, Leaves, refuse etc
· Maize stalk forming foundation.
Dry leaves on top.
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N/B: a long sharp pointed stick is driven into the pile at an angle. The stick is used for checking temperatures within the heap from time to time. If the temperature inside is high it can be corrected by adding water.
INORGANIC FERTILIZERS
Inorganic fertilizers are chemically made compounds processed for commercial use which are added into the soil to improve its fertility by providing one or more plant nutrients.
CLASSIFICATION OF INORGANIC FERTILISERS.
Fertilisers are classified in the following basis:
i. Nutrients contained.
ii. Mode of application.
iii. Time of application.
iv. Effects on soil Ph.
On the basis of the nutrients contained, the fertilisers are said to be either straight or compound (mixed).
i. Straight fertiliser.
This is a fertiliser that contains only one of the primary macro-nutrients. The nutrient contained may be Nitrogen ( N), Phosphorus (P), or Potassium (K). The fertilisers are named according to the nutrient they contain.
· Nitrogenous fertilisers: contain nitrogen as the only primary macro-nutrient, e.g Calcium Ammonium Nitrate (CAN), Ammonium Sulphate Nitrate (ASN), Sulphate of Ammonia (SA) and Urea.
· Phosphatic fertilisers: Contain phosphorus as the only primary macro-nutrient e.g Single Super Phosphate (SSP), Double and Triple Super Phosphate (DSP/TSP).
· Potassic fertilisers: contain potassium as the only primary macro-nutrient, e.g Potassium Chloride or Muriate of Potash (KCL) and Potassium Sulphate or Sulphate of Potash (K2SO4).
ii. Compound fertiliser.
A compound fertiliser is one that contains two or three primary macro-nutrients. It may also be referred as a complex or mixed fertiliser. When it contains only two of the primary macro-nutrients, the fertiliser is referred to as an incomplete compound fertiliser e.gDiammonium Phosphate (DAP) (18-46-0); 20-20-0 and others. When it contains all the three primary macro-nutrients, the fertiliser is referred to as a complete compound fertiliser e.g 20-10-10, 25-5-5+5s, 17-17-17 and 15-15-15.
PROPERTIES AND IDENTIFICATION OF FERTILISERS.
NITROGENOUS FERTILISERS
Characteristics of Nitrogenous fertilisers:
ü They are highly soluble in soil water.
ü They are easily leached to lower horizons.
ü They have a short residual effect.
ü They have scorching or burning effect on plants.
ü They are highly volatile.
ü They are hygroscopic i.e they absorb moisture from the atmosphere and cake.
ü They are highly corrosive.
PHOSPHATIC FERTILISERS
Characteristics:
ü They are sparingly soluble in water.
ü They have a residual effect.
ü They are not liable to leaching.
ü They have a slight scorching effect.
POTASSIC FERTILISERS
Characteristics:
ü They have a moderate scorching effect.
ü They have moderate solubility in water than phosphorus but less than nitrogen.
FERTILISER APPLICATION
Phosphatefertilisers are applied during the planting time while the nitrogen fertilisers are applied after the emergence of the crop.
METHODS OF FERTILISER APPLICATION
i. Broadcasting.
It involves the random scattering of fertilisers on the ground for plant use.
ii. Placement method.
This is the application of the fertiliser in the planting holes or drills.
iii. Side dressing.
This is the placement of nitrogenous fertiliser at the side of the crop being top dressed. It can be achieved by:
a. Band application.
b. Ring application method. It is the placement of fertiliser around an individual crop just beneath the edge of the canopy.
iv. Foliar spraying.
This is the application of specially formulated fertiliser solution onto the foliage of the crop.
v. Drip application.
This is where the fertiliser is dissolved and applied to individual plants, through perforated pipes or bottles.
DETERMINATION OF THE FERTILISER RATES
The amount of fertiliser applied in the field is determined by the amount of plant nutrients available.
Calculations Involving Fertiliser Application
1. Fertiliser Grade or Analysis
Fertiliser grade indicates the amount of each nutrient contained in a fertiliser. It is calculated by determining chemically the percentage of each nutrient present in a fertiliser that is;
Percentage of nutrient = Nutrient x 100/ Total weight of fertiliser.
Fertiliser grade is usually calculated in terms of the amount of the three primary macro-nutrient N.P.K. e.g a bag of 100 kg of fertiliser of a 10-10-10 grade contains 10 kg of N, 10 kg of P2O5 and 10 kg of K2O.
2. Fertiliser Ratio
It refers to the relative proportions of the three primary macro-nutrients (N.P.K) in a fertiliser. E.g a 10: 10: 10 grade has a 1:1:1 ratio of N: P2O2: K2O while a 20:10:10 grade would have a 2:1:1 ratio.
3. The amount of Fertiliser or Nutrient Required Per Unit Area ( per hectare)
The amount of fertiliser to apply per hectare depends on the amount of nutrients needed and the fertiliser grade available.
Example 1.
Suppose a soil is deficient in all the three primary macro-nutrients and in a field test it is found that the following should be applied: 60 kg N, 30 kg P2O5 and 40 kg K2O per hectare. Calculate the amount of sulphate of ammonia, superphosphate and Potassium Chloride required per hectare if the Ammonia areavailable are Sulphate of Ammonia (20% N), SSP (20% P2O5) and muriate of potash (50% K2O).
Solution:
i. If the soil requirement is 60 kg N/ha and the available fertiliser Sulphate of Ammonia containing 20% N, then the total amount of:
Sulphate of Ammonia (SA) is
= 60 kg N X 100 kg SA
20 Kg N
=300 kg SA.
ii. Total amount of SSP
= 30 kg P2O5 X 100 kg SSP
……………………………………………..
20 kg P2O5
= 150 kg SSP
iii. Total amount of K2O
= 40 kg K2O X 100 kg KCL
…………………………………………………….
50 kg K2O
= 80 kg KCL.
Example 2:
A farmer was advised to apply 150 kg CAN/ha, while top dressing the maize crop. CAN contains 21% N.
Calculate the amount of nitrogen applied/ha.
21 kg N is contained in 100 kg CAN.
150 kg CAN supplies:
100 kg CAN = 21 kg N
150 kg CAN = 21 kg N x 150 kg CAN
……………………………………….
100 kg CAN
= 31.5 kg N/ha.
CROP MANAGEMENT PRACTICES
MANAGEMENT PRACTICES
i. Gapping.
Gapping is the filling up or replacement of the dead seedlings. Gapping should be done soon after the crop has started growing to prevent excessive shading of the newly planted seedlings.
Reason:
ü Gapping ensures optimum plant population.
ii. Thinning.
Thinning is the uprooting or removal of the excess seedlings to allow space for the remaining seedlings.
Reason:
ü To obtain an optimum plant population in a given unit area.
iii. Pruning.
Pruning is the removal of extra or unwanted parts of a plant. The unwanted parts may be due to breakage, overcrowding, pest or disease attack and unproductivity.
Reasons for pruning
ü To train the plant so that it can have the required shape.
ü To remove the diseased and unwanted parts of a plant, such as extra suckers, leaves, branches, flowers or even stems.
ü It controls cropping.
ü To facilitate picking.
ü To ease the penetration of the spray.
ü It controls pests and diseases.
Methods of Pruning
a. Pinching out
This method involves the removal of terminal buds. It is a practice that is carried out in tomatoes (at a height of 1.6-1.8 m) and flue-cured tobacco after bearing 16-20 leaves.
b. Annual pruning.
It involves the removal of branches that have borne two crops and have undesirable growth characteristics. Those that are dry, broken, too close or diseased should be removed.
c. Coppicing or pollarding.
This is usually carried out in tree crops where branches are cut at specified points in order to achieve a desired shape.
iv. Staking and Trellishing.
v. Ratooning.
vi. Watering.
vii. Top dressing.
viii. Mulching.
Mulching is the placement of materials such as banana leaves, or polythene sheets on the ground next to the growing crop. These materials should not come into contact with the base of the crop as they may encourage pest attack.
Importance of mulching.
ü Reduction of evaporation rate.
ü Smothers weeds.
ü Moderation of soil temperature.
ü Reduction of speed of run off.
Types of mulching materials
There are two main types of mulching materials; namely:
i. Organic materials.
ii. Inorganic materials.
Organic mulching materials include sawdust, wood shavings, coffee pulps, rice haulms, dry grass, banana leaves, dry maize stalks, napier grass and any other vegetation that is not a weed to the crop.
Inorganic or synthetic materials commonly used are either black or transparent polythene sheets. These are usually used in highly profitable crops due to their high cost.
Advantages of Mulching
ü Prevents water evaporation thus maintaining moisture in the soil for crop use.
ü Acts as an insulator thus modifies or regulates the soil temperature.
ü Controls soil erosion by reducing the speed of running water, intercepting the rain drops and increasing the rate of infiltration.
ü Controls the weeds by suppressing their growth.
ü Organic materials are decomposed by soil micro-organisms resulting into humus that improves soil structure and water holding capacity.
ü Organic materials improve soil fertility by releasing nutrients after decomposition.
Disadvantages of Mulching
ü Provides a breeding ground as well as a hiding place for pests that finally may attack the crops.
ü Traps the light showers of rainfall thus lowering the chances of the raindrops reaching the soil.
ü It is a fire risk.
ü It is expensive to acquire, transport and apply.
CROP PROTECTION
WEEDS AND WEED CONTROL
A weed is any plant growing where it is not required and whose economic disadvantages outweigh the advantages. Some weeds are dangerous and their cultivation is prohibited by law, such weeds are called noxious weeds.
WEED IDENTIFICATION AND CLASSIFICATION
Identification
Weeds are identified by individual plant names. They are named according to specific features or a person who found them. Weeds are commonly identified using both common English names and vernacular names in some cases, these names are limited to small communities. The botanical names are preferred because they are recognised internationally.
These names have twoparts; the first part refers to the genus while the second part represents the species to which the weed belongs. They are usually written in italics or underlined. Names of common weeds in East Africa are given below for the purpose of identification.
|
BOTANICAL NAME |
COMMON NAME |
|
Amaranthus spp. |
Pigweed |
|
Achyranthesaspera |
Devil’s Horse Whip |
|
Cynogiossumcaerulum |
Forget-me-not |
|
Bidenspilosa |
Black jack |
|
Galinsogaparviflora |
Macdonald’s eye (Gallant soldier) |
|
Tagetesminuta |
Mexican marigold |
|
Tarchonathuscamphoratus |
Leleshwa |
|
Brassica napus |
Wild rape |
|
Cyperusrotundus |
Nut grass/sedge |
|
Digitariascalarum |
Couch grass |
|
Cynodondactylon |
Star grass |
|
Chlorispyrothrip |
False star grass |
|
Pennisetumclandestinum |
Kikuyu grass |
|
Eleusineindica |
Wild finger millet |
|
Avenafatua |
Wild oat |
|
Setariaverticillata |
Fox tail |
|
Oxalis latifolia |
Oxalis |
|
Strigahermontheca |
Striga |
|
Daturastramonium |
Thorn apple |
|
Solanumincanum |
Sodom apple |
|
Lantana camara |
Lantana (Tick berry) |
|
Solanumnigrum |
Black night shade |
|
Commelinabanghalensis |
Wandering jew |
|
Conyzabanariensis |
Fleabane |
|
Urticamassaica |
Stinging nettle |
Classification
Weeds can be classified either on the basis of growth cycles or plant morphology.
1. Growth Cycle
a. Annual weeds
These are weeds which complete their life cycle in the field within a period of one year or less. E.g. Mexican marigold, black jack, pigweed etc. Most annual weeds are easily controlled.
b. Biennial weeds
These are weeds which complete their life cycle in two years. They achieve vegetative growth in the first year and produce seeds during the second year. E.g. American wild carrot, Spear thistle, Ragwort etc.
c. Perennial weeds
These take more than two years or seasons to complete their lifecycles. E.g. Sedges, Lantana, Kikuyu grass, Wanderingjew, Couch grass, Sodom apple etc. These weeds are the most difficult to control.
2. Plant morphology
a. Narrow-leaved weeds
These are mostly grass weeds. They include Couch grass, Spear grass, Setaria, Eleusine etc. Grass weeds may be perennial or annual.
b. Broad-leaved weeds
These include weeds like Blackjack, Oxalis, Lantana, Pigweed, Devil’s horse whip etc. These weeds may be annual or perennial.
COMPETITIVE ABILITY OF WEEDS
These are factors which contribute to the competitive ability of weeds.
a. Weeds have extremely successful means of propagation. E.g.
· Ability to produce large quantities of seeds.
· Weed seeds remain viable in the soil for a long time waiting for conducive germination conditions.
· Most weed seeds are easily and successfully dispersed.
· Some weeds have ability to propagate vegetatively.
b. Weeds excellently adapted to the environment due to:
· Elaborate or extensive root system useful in supporting the plant, in nutrient absorption and water uptake.
· Ability to survive even where there is limited nutrient supply.
· Short lifecycle that is if the rain regime is restricted the plant is able to complete its lifecycle.
Harmful effects of weeds
Ø Chemical weed control contributes to environmental pollution.
Ø Weeds compete with crops for nutrients, space and light.
Ø Some weeds irritate or hurt workers.
Ø Aquatic weeds block river sources e.gsalvinia.
Ø Some weeds are alternate hosts of crop pests and diseases e.g wild oats –rusts..
Ø Some weeds are parasitic on crop plants e.gstriga spp.
Ø Some weeds are poisonous e.gdaturasramonium or thorn apple.
Ø Some are allelopathic.
Ø Some lower the quality of agricultural produce e.gTagetesminuta.
Beneficial effects of weeds
Ø Some weeds are edible to both man and livestock e.g pigweed, wandering jewetc
Ø Some weeds have medicinal effectse.g Sodom apple.
Ø Weeds act as soil cover, preventing soil capping due to the impact of the raindrops.
Ø Weeds add organic matter to the soil when they decompose.
Ø Leguminous weeds fix nitrogen in the soil.
Weed control measures
· Mechanical methods such as cultivation, tillage, slashing and uprooting.
· Cultural methods such as crop rotation, mulching, cover cropping, timely planting, use of clean planting materials, proper spacing, clean seedbed and flooding.
· Biological weed control method. This is where living organisms are used to suppress weeds as they feed on them. Such as use of livestock as goats to graze and control the growth of weeds in plantation crops like coconuts and cashew nuts.
· Chemical weed control method i.e use of herbicides.
Classification of herbicides:
Herbicides can be classified basing on the following aspects:
i. Formulation.
ii. Time of application.
iii. Selectivity.
iv. Mode of action.
v. Environmental factors.
Basing on formulation, herbicides are classified as:
Ø Liquids. These are liquid herbicides which are soluble either in water or in oil e.gDalapon and Paraquat.
Ø Wettable powders. These are finely ground particles mixed with water to form a suspension before application e.gAtrazines, Simazines and Duron.
On the basis of time of application, herbicides are classified as:
Ø Pre-emergence. These are herbicides which are applied soon after crop seeds have been sown but before they emerge. E.g. Atrazines and Simazines.
Ø Post-emergence. These are herbicides which are applied after crop germination or transplanting. Such as 2,4-D, M.C.P.A, Paraquat, and Glyphosate.
Basing on selectivity, herbicides can be classified as:
Ø Selective.
Ø Non-selective.
On the basis of mode of action, herbicides are classified as:
Ø Contact. These are chemicals which kill only the parts of the plant with which it comes into contact.
Ø Translocated or systemic. These chemicals kill the whole plant even if it has come into contact with only a small part of it. It is absorbed into the plant and is translocated to all parts of the plant.
Environmental factors such as rain, wind, soil, temperature or light may affect the effectiveness of a herbicide.
Advantages of using Herbicides
i. They require less labour than mechanical cultivation.
ii. They are better adapted to the control of certain bothersome weeds such as couch grass.
iii. Use of herbicides does not disturb crop roots and other underground structures.
iv. They make the control of weeds in certain crops such as wheat, barley and carrots easier.
v. Herbicide application is efficient in both wet and dry soil conditions.
vi. Herbicide application does not disturb the soil hence the soil structure is maintained.
vii. More convenient to use in certain crops such as sisal and sugarcane.
viii. It is cheaper in the long than the use of manual or mechanical cultivation.
ix. They are effective in controlling weeds such as double thorn and stinging nettle which may cause injury to the farmer.
Disadvantages
i. It requires skilled labour in mixing and application.
ii. There are many risks to the environment and the user.
iii. Some herbicides have long residual effects which may interfere with future crops.
· Integrated weed control method
· Legislative weed control. This method involves governmental laws and acts which prevent the introduction of noxious weeds in a country or spreading of foreign weeds from one part of the country to another.
DISEASES AND THEIR CONTROL
A disease is any alteration in the state of an organism or its parts, which interrupts or disturbs its proper performance or functions. It’s therefore any deviation from good health. Crop diseases are classified according to their causal agents, which include:-
(i) Fungal diseases.
These are diseases caused by fungi. Fungi are non-green plants incapable of manufacturing their own food due to lack of chlorophyll. They depend on other green plants or dead remains of plants and animals for their nutrition. Examples of fungal diseases include; late blight, rusts, smuts, CBD etc
(ii) Viral diseases.
These are diseases caused by viruses. Viruses are extremely small living organisms which can only be seen under a very powerful electronic microscope. All viruses are parasitic and are only able to multiply in living tissue. Viral infections interfere with the vital life processes of a plant such as photosynthesis, respiration, transpiration and nitrogen utilisation. Symptoms of viral infections include:
- Leaf chlorosis.
- Leaf curling.
- Mosaics.
- Malformations (distortion)
- Rosetting.
Viral diseases are transmitted through the use of infected vegetative materials and insect vectors such as aphids, mealybugs or leafhoppers.
Examples of viral diseases:
i. Groundnut rosette.
ii. Cassava mosaic.
iii. Tobacco mosaic.
iv. Potato leaf-roll.
v. Greening disease of citrus fruits.
vi. Brown streak of cassava.
(iii) Bacterial diseases.
These are diseases caused by bacteria. Bacteria are microscopic single-celled organisms which reproduce by binary fission. Bacteria are able to live on both living and dead tissues. They are transmitted through irrigation water, seeds, fertilisers, manures, wind, raindrop splashes, insects, soil and mechanical means such as through cultivation implements and pruning knives.
Symptoms of bacterial diseases:
Ø Wilting even when the water is in adequate supply due blockage of xylem vessels by masses of bacteria.
Ø Cankers. These are localised infections which result in death of the plant tissues (necrotic tissues).
Ø Gall formation in the infected tissues.
Examples of bacterial diseases:
i. Bacterial blight of coffee.
ii. Halo blight of beans.
iii. Black rot of cabbage.
iv. Black arm of cotton.
v. Bacterial wilt of potatoes and tomatoes.
(iv) Nutritional disorders.
When crops do not get enough nutrients, deficiency symptoms may appear. i.e Nutritional disorders.
Deficiency symptoms:-
Ø Yellowing of leaves.
Ø Drying of leaves.
Ø Falling of leaves, flowers and fruits.
Ø Stunted growth.
Ø Death in extreme condition.
Ø Formation of anthocyanins.
Other causes of plant diseases are:
· Flooding. On flooded condition, ammonia which is poisonous to plants may be formed; it has a burning effect on leaves.
· Chemicals. Some toxic chemical compounds in the soil may be absorbed by the plants, leading to death of the plant.
· Poor weather. Extremes of day and night temperatures may cause hot and cold disease in coffee (Elgon die back).
· Stress. Stressful conditions on the plant such as irregular watering may cause physiological disorders such as blossom-end rot in tomatoes.
Harmful effects of crop diseases
· Lowering crop yields.
· They cause the production of poor quality products thus reducing their market value.
· Control of diseases increases the cost of production.
· They cause food poisoning for example ergot in wheat, barley and rye causes nerve poisoning. Aflatoxin which is produced by the fungus aspergillus spp. Growing on moist stored grains is poisonous and can cause death if such grains are consumed.
· Environmental pollution resulting from the use of chemicals in the process of controlling the diseases.
Control of crop diseases.
Ø Cultural methods.
These are crop husbandry practices which are used to control diseases without the use of chemicals. They include:
- Healthy planting materials.
- Proper seedbed preparation.
- Heat treatment.
- Field hygiene.
- Diseases resistant varieties such as Ruiru 11, a coffee variety resistant to Coffee Berry Diseases.
- Proper spacing controls damping off in cabbages.
- Proper drying of the cereals.
Ø Legislative method
It involves imposing of regulations and laws especially in cases of disease outbreaks to prevent the introduction and spreading of diseases.
Ø Chemical control.
Chemical disease control should be practiced only when other methods have been deemed ineffective and when it is economical.
They include:-
- Seed dressing. This is the application of fungicides before planting seeds.
- Soil fumigation. This is the application of fumigants in the soil to control soil borne diseases such as bacterial wilt in potatoes.
- Spraying. The application of fungicides using a sprayer to control such diseases as CBD, Blights, Rusts etc.
CROP PESTS AND THEIR CONTROL
A crop pest is defined as a living organism that destroys crops either directly by causing physical damage to the plant or indirectly by introducing disease-causing organisms, or pathogens into the plant. Examples of the pests are:- Insects as hoppers, Rodents e.g rats, mice, squirrels, Nematodes e.g worms, Mites, Aphids and Large animals such as monkeys, elephants, buffaloes etc.
Harmful effects of crop pests
- Pests such as squirrels and mice unearth planted seeds resulting in low plant population.
- Some pests such as nematodes, termites and moles damage crop roots causing wilting and death to the plants.
- Pests destroy crop leaves lowering the photosynthetic area resulting in reduced yields.
- Sucking pests deprive the plant its food by sucking plant sap resulting in retarded growth.
- Some pests attack fruits, berries, flowers, thus lowering their quality and quantity.
- Some pests destroy the embryo of seeds, thus lowering their germination potential.
- Some pests transmit crop diseases while others open up the plant to secondary infection.
- In crops where the leaf is the major product, for example kale, pest damage lowers the quality and quantity through defoliation.
- Pests reduce the marketability of crop produce by lowering quality. Weevils for example, bore into maize grains, thus lowering their economic value.
CLASSIFICATION OF PESTS
Pests are classified according to:
i. Their mode of feeding.i.e pests with biting and chewing mouth parts, and those with piercing and sucking mouth parts.
ii. Crops attacked.i.e coffee pests, maize pests etc
iii. Stage of development of the pest.i.e larval or nymphal or adult.
iv. Stage of growth of the crop attacked.
v. Scientific classification. i.einsects, birds, nematodes, mites etc.
vi. The level of damage. i.e minor pests and major pests.
vii. The place where they are found or habitat. i.e field pests and storage pests.
IDENTIFICATION OF COMMON PESTS
1. Field pests which includes;
· Insect pests.
|
Pest |
Crop attacked |
Disease transmitted |
|
Aphids (Aphis crassivora) |
Groundnut |
Groundnut rosette virus |
|
Aphids (Myzuspersicae) |
Groundnut |
Groundnut mosaic virus |
|
Aphids (Myzuspersicae) |
Tobacco |
Tobacco mosaic virus |
|
Tobacco whitefly (Bimisiatabaci) |
Tobacco |
Tobacco leaf curl virus |
|
Tobacco whitefly (Bimisiatabaci) |
Cassava |
Cassava mosaic virus |
|
Pineapple mealy-bug (Dysmicoccusbrevipes) |
Pineapple |
Pineapple virus |
The table above shows some sucking insects and the viral diseases they transmit.
· Mites.
· Nematodes.
· Rodents. These are gnawing animals such as mice, rats, squirrels, porcupines, hedgehogs and moles.
· Birds such as Sudan Diouch, Mouse bird, Domestic fowl and weaver bird.
· Large animals such as elephants, buffaloes, monkeys, apes, wild pigs, antelopes and hippopotamuses.
2. Storage pests which include;
· Rodents.
· Insects.
|
Species |
Scientific Name |
Stored crop affected |
|
Weevil |
Sitophilusspp |
Maize, Sorghum, Wheat, Rice |
|
Lesser grain borer |
Rhizoperitadominza |
Rice, Maize, Wheat |
|
Khapra beetle |
Trogedermagrananium |
Maize, Wheat, Pulses, Sorghum |
|
Saw-toothed grain beetle |
Oryzaephilus spp. |
Maize, Wheat, Groundnut |
|
Pulse beetles |
Callosobruchusobtectus |
Beans |
|
Flat beetles |
Laemophiloeuspusillus |
Grain flour |
|
Agoumois grain moth |
Sitotragacerealella |
Maize, Wheat |
|
Tropical/warehouse moth |
Ephestiacoutelle |
Rice, Maize, Wheat |
|
Potato tuber moth |
Pthorimaeaoperculella |
Stored Irish potatoes |
· Fungi.
CONTROL OF CROP PESTS
If pest population causes damage beyond tolerance, it is said to have reached economic injury level (EIL). Control measures should be affected before this level. Pest control methods include:
i. Legislative method/ Quarantine
This is a government regulation stating that any planting materials from other countries or areas known to have pests must be tested before they are accepted for planting.
ii. Physical measures.
They include:
ü Use of lethal temperatures.
ü Proper drying of produce.
ü Flooding.
ü Suffocation.
ü Use of scarecrows.
ü Physical destruction.
ü Use of electromagnetic radiation i.e certain wavelengths of electromagnetic radiations may be used to deactivate enzymes in some insects. For example, moths are attracted by ultra-violet and aphids by yellow light.
iii. Cultural methods
These include all farming practices employed to alter the environment making it unfavourable for the survival of pests, hence allowing the crop to escape injury. These include:
ü Timely planting.
ü Timely harvesting.
ü Proper tillage.
ü Close season. This is a period when a susceptible crop is not grown in order to control a certain pest or group of pests.
ü Trap cropping. A trap crop is one which is planted before or together with the main crop purposely for attracting pests away from the latter.
ü Crop rotation.
ü Resistant varieties.
ü Field hygiene.
ü Alteration of environmental conditions. Creation of certain micro-climates that is not conducive to some pests. Open pruning in coffee discourages antestia bugs, while mulching reduces thrips.
ü Crop nutrition.
ü Destruction of alternative hosts.
ü Use of clean planting materials.
ü Proper spacing.
ü Use of organic manure. FYM manure has been found to discourage various pests, particularly eelworms.
ü Irrigation. Overhead irrigation is known to control aphids in cabbages.
iv. Chemical control measures
This is the use of pesticides to control pests. The pesticides used should be efficient, selective, safe to the user and the environment, persistent and cheap.
v. Biological pest control
It involves the use of living organisms to control pests. It is based on predator-prey relationships. A predator is a living organism that kills another for food while a prey is a living organism that is killed by another for food. E.g. known predator-prey relationships:
|
Predator |
Target pest |
|
Ladybird |
Aphids |
|
Wasps |
Coffee mealy bugs |
|
Praying mantis |
Giant looper |
|
Majimoto ants |
White scales |
|
Chicken |
Cotton strainers |
|
Cats |
Moles, rats, mice |
|
Chameleons |
Most insects |
CROP ROTATION
Crop rotation is the growing of different types of crops or crops of different families on the same piece of land in an orderly sequence. It is made possible by sub-dividing the land into plots. In each of these plots different crops are grown in a particular season. In the following season the crops are rotated or grown in the next plot. This practice is commonly carried out in annual crops.
In designing a good crop rotation, the farmer must decide what crops to have in the rotation, in what sequence the crops should occur, and for how many years or season each cycle of the rotation must run. A good rotation that provides for maintenance or improvement of soil productivity usually includes a legume crop to promote fixation of nitrogen, a grass or legume sod crop for maintenance of humus, a cultivated or inter-tilled crop for weed control and fertilizers.
|
Family |
Crops |
|
Solanacea (potato family) |
Tomatoes, Irish potato, Brinjals, Tobacco |
|
Graminae (grass family) |
Maize, Sorghum, Wheat, Barley, Rice, Sugarcane |
|
Leguminosae (Legume family) |
Beans, Peas, Groundnuts, Lucerne |
|
Cruciferae (Cabbage family) |
Cabbages, Kales |
Season/Year 1
|
Plot A |
Plot B |
|
Maize |
Beans |
|
Plot D |
Plot C |
|
Sweet potatoes |
Cabbages |
Season/ Year 2
|
Plot A |
Plot B |
|
Sweet potatoes |
Maize |
|
Plot D |
Plot C |
|
Cabbages |
Beans |
IMPORTANCE OF CROP ROTATION
This is a cultural practice which is recommended for the following reasons:
i. Maximum utilisation of nutrients.
Different crops vary in their nutrient requirements in terms of type of nutrient and the depth of absorption. For example, maize plant absorbs a lot of nitrogen from the soil but low amount of potassium. Cassava on the other hand needs a lot of potassium but low amount of nitrogen. Alternating maize with cassava, therefore leads to the maximum or better utilisation of these nutrients.
ii. Control of soil-borne pest and disease build-up.
Some pests and diseases are specific to various crops. Such pests and diseases will always attack crops of the same family when grown in succession. To control them such crops should be alternated with crops from different families.
iii. Control of weeds.
Parasitic weeds such as witch weed (strigaspp), which are specific to grass family crops, can be controlled by planting non-grass crops for a period of time.
iv. Improvement of soil fertility.
When leguminous crops are included in the rotation programme, they help in improving the soil fertility through fixation of nitrogen with the help of the Rhizobia bacteria.
v. Improvement of soil structure.
Establishment of a grass ley in the rotation programme leads to little disturbance of the soil at the same time, roots of grasses are so extensive that they bind soil particles together thus improving the structure.
vi. Control of soil erosion.
Crops planted in rows such as maize, should always be alternated with cover crops to control erosion.
vii. It offers the farmer some insurance against crop failure, and enables him to spread out his labour needs.
Factors that affect crop rotation
The choice of a rotation for a particular farm depends upon the following:
1. Adaptation of the crops to a particular soil, climate and economic conditions.
2. Prevalence of weeds, plant diseases and insect pests may also limit the kinds of crops that can be grown in a locality.
3. Crops may be selected for rotation so as to spread labour throughout the year.
Principles of crop rotation (Factors to consider in deciding the sequence of crops)
i. Crop root depth
Deep rooted crops should be alternated with shallow rooted crops.
ii. Crop nutrient requirements
Heavy or gross feeders should come first in a newly opened land which is relatively fertile.
iii. Weed control
Crops which are associated with certain weeds should be alternated with those that are not. Crops that are not easy to weed should be alternated with those that are easily weeded.
iv. Pest and disease control
Crops from the same families should not follow one another in the rotation programme as they are attacked by the same pests and diseases.
v. Soil fertility
Leguminous crops should be included to improve soil fertility.
vi. Soil structure
When the soil is used continuously, it becomes loose and pliable; a grass ley should be included in the soil structure. The grass ley should be allowed a duration of 3-6 years.
vii. Deep-rooted crops should be alternated with shallow rooted crops.
Factors determining the choice of the rotation programme
ü Type of the soil
ü Prevailing climatic conditions in the area.
ü Economic consideration of merits and demerits of crop systems.
ü Crops adapted to a particular area.
ü Personal tests and preferences of a farmer.
ü Incidences of pests and diseases.
Limitations of crop rotation
ü The growing of one crop means that the demand for labour occurs in peaks. Labour demand is more evenly spread if many crops are grown simultaneously.
ü The risk of crop failure is ever present, and the risk is greater where only one crop is grown.
ü Since each crop occurs on the farm only once every several years, specialized facilities for the target crop, can only be utilized once in several years, a situation which is definitely inefficient.
ü There is scarcity of land.
CROPPING SYSTEMS
INTRODUCTION
Sustainable agricultural systems imply successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources. High productivity is an important aspect of agricultural sustainability in the humid regions.
CROPPING SYSTEMS
The term cropping system is used to describe the pattern in which crops are grown in a given area over a period of time and includes the technical and managerial resources that are utilized.
CLASSIFICATION OF CROPPING SYSTEMS
Cropping systems are classified basing on the following criteria:
1. The distribution of crops in time i.e whether shifting cultivation, continuous cropping, monoculture or crop rotation is practised.
2. The distribution of the crops in space on the field i.e whether intercropping or sole cropping is practised.
3. The level of management and resources utilized to produce the crop i.e whether production is intensive or extensive.
4. The type of crop grown i.e whether orchard, arable cropping, pasturing, forestry etc is practised.
CROPPING SYSTEMS
1. Shifting cultivation
This is where a piece of land is cleared, farmed for a few years and then abandoned in preference for a new site. While the new site is being farmed, natural vegetation is allowed to grow on the old site. Eventually, after several years of bush fallows, the farmer returns to the original location.
Advantages of shifting cultivation
v It has low capital investment.
v Self-sustaining and therefore for simple farmers is convenient if other issues are not important.The self-sustaining depends on:
- Recycling of nutrients
- Fallen leaves add a lot of organic matter and nutrients.
v Forest and/or savannah provide good soil cover.
v Reduced leaching under the fallow.
v Reduced losses due to pests and diseases.
v No land disputes as land ownership is not individualized.
Disadvantages of shifting cultivation
v Difficult to increase productivity of labour and land i.e it is extensive and difficult to intensify thus low productivity.
v A lot of time is wasted when the farmer is shifting and building structures.
v Farmers have no incentives to develop land and conserve water and soil.
v Not applicable in areas of high population density or where there is a high population increase.
v It tends to discourage high level of inputs.
2. Monoculture/single cropping/Monocropping
This is a practice of instantly cultivating the same type of crop on the same piece of land year after year.
It is also a practice of repeated growing of crops on the same field each year at the same time onr one after another or a continuation of both.
Limitations of monocropping
v Crops which are grown become highly susceptible towards pests and diseases; which bring about crop failure.
Advantages of monocropping
v It allows for plant adaptation to changing soil condition because of difference in quick demand by the evolving crops for nutrients and water.
v It facilitates vertical and horizontal variation thus allowing cultivation of crops that may be adopted to light and shed.
v It permits phased harvesting and distributing of workload.
v It provides reasonable soil cover which protects soil erosion while supressing weed growth.
v It provides higher total yields and the land itself become adapted to small scale hand operated farming.
3. Multiple cropping i.e intercropping and sequential cropping
Intercropping
This is a system that involves the growing of two or more crops on the same field at the same time. This can be:
a. Mixed intercropping –growing of two or more crops simultaneously with no distinct row arrangement.
b. Row intercropping – growing two or more crops simultaneously with one or more crops planted in rows.
c. Strip intercropping – growing two or more crops simultaneously in different strips wide enough to permit independent cultivation but narrow enough for crops to interact agronomically.
d. Relay intercropping – growing two or more crops simultaneously during part of each other’s cycle i.e second crop planted after first crop has reached its reproductive growth but before its ready for harvest.
Advantages of intercropping
v There is yield advantage in growing crops together than growing each one separately.
v There is a more efficient utilization of the resources available.
v The component crop may complement each other in their use of space.
v An intercrop may be able to utilize resources which the main crop may not be able to utilize or which may even be disadvantageous to it.
v Certain crops may exert specific beneficial effect on others.
v The farmer is more or less buffered against failure of one of the crop.
v Intercropping allows for a more uniform distribution of labour throughout the year.
v The spread of diseases and pests is less rapid than in sole cropping.
v When one component of an intercrop combination fails, the other combinations are able to utilize the resources that would have been available to the failed crop, and so yield better than they would have done otherwise.
Disadvantages of intercropping
v Since many crops exist together on the field, it is not possible to tailor production practices to the needs of any particular crop.
v Control of pests and diseases is particularly difficult.
v It is difficult to mechanize operations such as planting, weeding and harvesting.
Sequential Cropping
This is the growing of two or more crops in sequence on the same field per year. This can be done as:
a. Double cropping – growing two crops a year in sequence.
b. Triple cropping – growing three crops a year in sequence.
c. Quadruple cropping – growing four crops a year in sequence.
d. Ratoon cropping – cultivation of a crop re-growth after harvest e.g. sugarcane.
4. Agro-forestry systems
Agro-forestry systems involve growing woody herbaceous species and perennials in association with food crops and livestock on the same piece of land.
They are known to increase ecological diversity within a landscape unit and optimize the use of limited resources through the integration of complementary components.
Disadvantages
v The yield of individual components may be decreased probably due to allelopathic effects
v Yield reduction may also happen due to competition for nutrients between perennials and animals
v High labour requirements is another limitation of agroforestry systems
v The systems is labour-intensive and complete mechanization is often difficult and not feasible to achieve.
STAPLE FOODS
MAIZE
Maize is the staple food in most areas of Kenya. It is also a very important feed for livestock. It is processed in industries to produce oil and starch. Large scale maize production goes on in Trans Nzoia, Nakuru and Uasin Gishu districts.
ECOLOGICAL REQUIREMENTS
i. Altitude – 0 – 2200 m above sea level.
ii. Temperatures - maize prefers medium temperatures.
iii. Rainfall -
iv. Soil - Fertile alluvial or loam soils which are free draining.
Soil pH should be neutral or alkaline.
Maize is drought resistant during the early stages of growth and does not require much rain towards maturity but, it must have enough rain at silking stage.
VARIETIES
Several hybrids and composites are produced in various research stations like the National Research Station i.eKitale, Embu Research Station, Katumani Research Station Machakos and Coast Agricultural Research Station – Mtwapa.
Hybrids are bred by crossing inbreed lines or varieties under conditions of controlled pollination. Composites are bred growing a number of varieties together under uncontrolled pollination, there is free inter pollination.
These hybrids and composites are produced for specific altitudes in the country. For example, Kitale hybrids include; 614, 622, 625, 626, 627 and 632. They are generally grown in medium to high altitude zones. Embu hybrids include 511 and 513, they grow best in medium altitude zones. Katumani composites have been developed for lower altitude zones. Coast composites, Pwani hybrid 1 and Pwani hybrid 4 have been developed at the Coast Agricultural Research Station – Mtwapa for Coast province. Others include double cob varieties for example DH01 and DH02.
SELECTION AND PREPARATION OF PLANTING MATERIALS
Kenya Seed Company contracts specific farmers to grow maize for seed. Maize is then harvested and treated using Thiram-dindane to prevent pest attack and sold to farmers as seed. Farmers are advised to buy fresh seed for planting every season. This is because of the problem of reduced hybrid vigour in the first generation.
LAND PREPARATION
Maize should be grown on a land prepared early enough to allow stubble enough time to rot. Ploughing is done using disc or mould board ploughs. Harrowing is done where the seedbed is rough, although a fine seedbed is not necessary for maize.
Maize does well when grown in rotation with other crops such as beans, tobacco, cotton, groundnuts and irish potatoes. Maize takes a lot of fertility out of the soil. Continuous cropping of maize should be avoided unless the soil is very fertile or where a lot of fertilisers are applied.
FIELD OPERATIONS
i. Planting.
Planting should be done quite early in the rains so that the crop can make maximum use of available moisture. Dry planting should be practised in areas with short rainy seasons. Time for planting always reduces yields. Early planting also reduces attack by stalk borers.
The depth at which seeds are placed varies from 2.5 cm to 10 cm. seeds are placed shallowly in moist soils and deeply in dry soils, such as when dry planting is done.
One or two seeds are placed in every hole.
The spacing is 20 cm to 30 cm by 75 cm to 90 cm. the spacing depends on the ecological conditions and the cultivars to be planted.
Planting is done by hand on small farms, while tractor-drawn planters are used on large farms.
ii. Fertiliser Application
Fertiliser application starts at the time of planting when 100-150 kg of double super phosphate per hectare is applied. Other compound fertilisers can be applied at the time of planting, for example 20-20-0 is used at the rate of 200 kg/hectare. Organic manures also give good responses. Some nitrogenous fertilisers such as C.A.N is top dressed when the maize is about 45 cm or knee high. In some cases the nitrogenous fertiliser can be split so that one half is applied when the plants are 45 cm high and the other half, just before tasselling. 200 kg of A.S.N orC.A.N are applied per hectare.
iii. Weed control.
Weeds in maize should be controlled right from the early stages of growth to reduce competition for moisture and nutrients. Two to three weedings would give the crop a chance to grow properly to the point where it can suppress the weeds. Hand weeding is mainly practiced. Herbicides can also be used, for example simazine, and triazine which are applied before the crop germinates and MCPA and 2, 4-D which are applied after the crop has emerged.
iv. Pest and Disease Control
PESTS
a) Field Pests
i. Maize stalk borer (Buseolafusca)
This is a larval stage of a moth which attacks maize from the early stages of growth. It makes holes in the leaves, resulting in windowing.
Control:
ü Early planting.
ü Rogueing.
ü Burning infected maize crop remains after harvesting.
ü Pesticides such as endolsulfan, diazinon, dipterex, malathion and stalk borer dust, may be applied down the funnel of each plant when it is about 30 cm high.
ii. Army worm ( Spodopteraexempta)
Army worms are larvae of a moth. The caterpillars are greyish-green in colour with characteristic black stripes at the back and both sides. They cause damage by eating the leaves, thus causing defoliation. Only midribs are left.
Control: Dusting with malation, diazinon etc.
iii. Aphid (Rhopalosiphummaidis)
This pest sucks sap from the green husks of cobs and leaves. The attacked leaves and husks appear black in colour.
Control:Spraying the crop with insecticides such as diazinon, malathion etc.
iv. Birds.
These eat the grains at the milky stage. The removal of husks by birds allows water to get in and cause rotting.
Control: Use of scare crows.
b) Storage pests
i. Maize weevil (Sitophiluszeamais)
It makes tunnels beneath the seed coat and circular holes on the surface of the grain.
Control:
ü Dusting the maize cobs or shelled maize with malathion.
ü Stored maize can also be fumigated with methyl bromide.
ü Proper storage hygiene (sweeping and removing old crops) is also effective in weevil control.
ii. Red Flour Beetle (Triboliumcastaneum)
This is a small reddish-brown beetle which feeds on flour and previously damaged and broken grains.
Control: Proper storage hygiene.
iii. Rats (Rattusrattus)
They attack stoked and fallen maize in the field, but they are more serious pests in the store.
Control: Use of rat proof stores, cats, traps and poisoned baits. Bush clearing around stores discourages rats.
DISEASES
i. White Leaf Blight
This is a fungal disease caused by the fungus Helminthosporiumturcicum. It causes oval, grey and thin lesions on the leaves.
Control: Planting resistant varieties.
ii. Maize Streak
This is a viral disease spread by grasshoppers. It causes yellow longitudinal stripes which run parallel to the midrib.
Control: Use of certified seeds, early planting, uprooting and burning affected plants to prevent further spread.
iii. Rust
It is caused by Pucciniasorghi and Pucciniapolysora. It forms red or brown pustules on the leaves.
Control: Planting resistant varieties.
iv. Smut
This is a fungal disease caused by the fungus Ustilagozeas. It destroys grains and tassels, causing masses of black powder.
Control: Crop rotation.
HARVESTING
The period between planting and harvesting of maize varies depending on the altitude and variety planted. Therefore, maize takes between three and nine months. Stalks are cut and stoked in the field to allow the cobs to dry properly. The cobs are then removed by hand and placed in the store. De-husking directly in the field without first stoking is common. Harvesting can also be done using combine harvesters.
Harvesting is done when the grains have 20% moisture content and then sun dried to 12% moisture content before storage.
The maize stalks are then ploughed in the soil, in most farms, this helps in returning some of the nutrients such as potassium and calcium into the soil.
Yields of 3,000 kg to 4,500 kg per hectare can be obtained.
STORAGE
Maize can be stored on cobs or it can be shelled and bagged. The stores should be properly constructed to keep out moisture and pests like rats. Proper store hygiene should be observed to prevent losses through pests, diseases and other damages. The seeds should be dried properly to reduce the chances of rotting and also minimise the extent of insect damage.
MARKETING
The National Cereals and Produce Board purchases shelled maize and stores it in large stores which are found in many parts of the country. Private buyers purchase maize directly from the farmers due to liberalisation in marketing. Maize dealers such as millers and livestock feed companies obtain their maize supplies from the board. Large consumers like institutions also purchase their grains from the board.
WHEAT
AGROFORESTRY
Agroforestry refers to land use practices in which trees or shrubs (woody perennials) are grown together with crops or pasture. This association has both ecological and economic benefits. It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy and sustainable land use systems.
SYSTEMS/FORMS OF AGROFORESTRY
The main components of agroforestry systems are trees or shrubs, crops, livestock and pastures. The systems or forms of agroforestry can be classified according to the main components present.
1. Agrisilvicultural
This system involves simultaneously growing crops and trees on the same piece of land. The piece of land may be as smell as half hectare or as big as thousands of hectares. During this period, insects, pests, diseases and weeds associated with the previous crops are controlled. The land also regains its fertility through leaf fall and decay and erosion. Recycling of leached nutrients back to the top soil also takes place.
2. Agrisilvopastoral
This system involves a three-way mixture based on a combination of crops, trees and animals. This system requires skilful management, and can be sustainable even in harsh environments and fragile soils.
3. Silvopastoral
This system involves raising livestock on improved pastures grown in association with trees and shrubs. It can be practiced on small farm or a large rangeland. Large scale silvopastoral system on rangeland involves cutting down unwanted trees and shrubs and selective protection and management of naturally growing trees and shrubs. The trees provide shade and fodder to the livestock as well as other uses to the farmer.
4. Entomoforestry
In this system insects are reared within trees and shrubs. Silkworms, for example, are reared using mulberry trees to produce silk.
5. Apiforestry
This involves deliberate growing of certain species of trees and shrubs to provide nectar or pollen for bees to make honey.
6. Aquaforestry
This is the growing of trees or shrubs to provide forage or breeding places for aquatic animals.
IMPORTANCE OF AGROFORESTRY
Agroforestry has many benefits to the farmer depending on the form in use. Some of the benefits include the following:
a. Conservation of soil and water
Agroforestry helps to conserve soil and water through the ground cover, and root system, to protect soil from erosion and improve soil fertility. The effect of agroforestry also increases the seasonal availability of water for plant growth.
b. Shelters
Trees provide shade and shelter for animals. They also give protection to wildlife from adverse weather. Trees and shrubs act as home to wildlife and give them protection.
C. Cash income
Through the sale of agroforestry products, farmers get extra income. Some people are also employed in tending trees and earn monthly salaries.
D. Medicine
Trees and shrubs provide herbal medicines which can cure various human and livestock diseases. For example, barks of cinchoma trees are used to produce quinine for curing malaria.
E. Raw materials for crafts
Trees provide materials for carving craft items which can be sold locally or exported.
F. Energy supply
Trees provide wood fuel used to supply energy for various uses including cooking, warming or boiling water.
G. Food supply
Fruit trees like mangoes when included in agroforestry provide fruits which supply the much needed vitamins and other food values.
H. Savings and investment
By establishing a woodlot or an orchard, a farmer is investing for the future. This is better than saving the money as the investment appreciates much faster.
I. Animal fodder
High protein trees like Calliandracalothyrsus provide valuable fodder for livestock. The fodder can be used to supplement normal grazing or can be used during dry seasons.
J. Pollen and nectar
Trees and shrubs provide valuable pollen and nectar which bees use to make honey, propolis and royal jelly. Apiaries are usually located in woodland which not only provides nectar and pollen but also shelter for the bee hives. Bees get excited if they are overheated and may even swarm away.
K. Improvement of soil fertility
Agroforestry trees planted with crops or in rotation with crops improve soil fertility. The leaves that drop decay and increase organic manure in the soil. The trees also recycle the nutrients from the lower soil horizons where crop roots cannot reach. The nutrients are recycled back to the top soil for use by crops.
L. Provide building materials
Trees provide timber and poles used for building and making furniture. Various types of farm structures are built of wooden materials.
M. Used as windbreak
Trees planted around the crop field protect the crops from being damaged by strong wind. They also protect buildings and other structures from wind damage.
N. Improves micro-climate
Trees improve micro-climate suitable for the growth of crops. For example, trees grown inside a coffee plantation create a cool climate suitable for coffee growth.
Important trees and shrubs and their uses
1. Cassia siamea
2. Casuarinaequisetifolia
3. Acacia albida
4. Azadirachtaindica
5. Gmelinaarborea
6. Grevillearobusta
7. Leucaenaleucocephala
8. Acacia Senegal
9. Markhamialutea
10. Cajanuscajan
11. Calliandracallothyrsus
12. Croton macrostachyus
13. Gliricidiasepium
14. Sesbaniasesban
15. Cordia Africana
16. Erythrinaabyssinica
17. Fruit trees such as citrus, guava, loquat, mango etc
TREE NURSERY
DEFINITIONS:
1. Seedbed
This is a piece of land which has been prepared ready to receive planting materials.
2. Nursery bed
This is a special nursery bed prepared for raising seedlings before transplanting.
3. Seedling bed
This is a special type of nursery bed used for raising seedlings which have been removed from the nursery bed due to overcrowding before they are ready for transplanting.
4. Nursery practices
This refers to all activities carried out during the preparation and management of a nursery bed to raise planting materials.
Importance of nursery beds
v They facilitate production of many seedlings in a small area.
v Routine management practices are easily and timely carried out.
v They make provision of best conditions for growth, such as fine tilth, levelled field and shade possible.
v They facilitate the planting of small seeds which develop into strong seedlings that are easily transplanted.
v They ensure transplanting of only those seedlings that are healthy and vigorously growing.
v They facilitate transplanting of seedlings that are already established thus reducing the period taken in the field.
v Excess seedlings from the nursery may be sold, thus become a source of income to the farmer.
Factors considered when selecting a nursery site
v Nearness to the water source.
v Type of soil.
v Topography.
v Previous cropping.
v Security.
v Well sheltered place.
Establishment of vegetative propagation nurseries
ü Select the suitable site.
ü Clear and level the site.
ü Establish vegetative propagation unit measuring 3.66m by 1.22m.
ü Fill polythene sleeves measuring 7-10 cm in diameter and 23-30 cm long with a rooting mixture.
ü Water the sleeves.
ü Insert the cuttings seedling at the centre of each sleeve. Arrange the sleeves in the vegetative propagation unit.
ü Erect wooden loops over the sleeved cuttings.
ü Place polythene sheet into the ground at the edges.
Nursery management practices
v Mulching.
v Watering.
v Weed control.
v Pricking out.
v Shading.
v Pest and disease control.
v Hardening off.
Care and management of trees
After transplanting tree seedlings, they should be properly cared for and managed until they grow into big trees. As they grow big the amount of care decreases. The following care and management practices are important:
I. Weeding – proper weeding should be done to remove weeds by light cultivation when the seedlings are still young. As they grow bigger only the area around the base of the trees should be weeded.
II. Mulching – seedlings planted in dry areas should be mulched using either dry organic mulch or synthetic mulch materials.
III. Protecting seedlings – individual seedlings should be protected if they are planted where livestock or wild animals can destroy them. This is done by erecting stakes or constructing wire fence around each seedling.
IV. Watering – young seedlings should be watered regularly depending on the rainfall pattern area.
V. Application of insecticides–the seedlings may be attacked by insects which not only impair their growth but may also kill them depending on severity of attack and the age at which they are attacked.
VI. Applying fungicides – Fungicides should be sprayed onto the seedlings or trees to stop the spread of the fungal diseases.
VII. Pruning and training – as trees grow; they should be pruned and trained to grow into a desirable shape. In branch pruning the branches are cut to shape the foliage as desired. In root pruning lateral roots that would compete with crops or interfere with structures are cut. A trench is dug to expose the roots at an appropriate distance from the tree line and the exposed lateral roots cut in clean angled cuts.
VIII. Grafting – grafting is the art of joining parts of plants together in such a manner that they will unite and continue to grow as one plant. It helps to perpetuate plants that cannot be conveniently reproduced by cuttings, layering or other asexual means. Grafting enables farmers to get the benefits of plants species with desirable root characteristics.
IX. Trapping moles–where there are many moles, traps can be laid in their underground tunnels to catch them. Moles usually destroy trees by eating their roots.
Transplanting of trees
Sites for agroforestry trees
a. Boundaries
Trees and shrubs are usually planted to demarcate boundaries. However trees also provide useful products, offer protection and help in soil and water conservation, as well as adding aesthetic value to the farm. Trees meant to demarcate boundaries are planted at different spacing from those meant for live fence and whose aim is to act as physical barriers.
b. River banks
Land adjoining the river is normally exposed to soil erosion particularly during rainy seasons or when there is a heavy downpour. During such times the river overflows its banks and flood water is likely to carry away large volumes of soil from the banks. It is therefore recommended to plant trees along river banks including trees, grasses and shrubs combined together resist soil erosion along the river banks, streams, ponds or lakes.
c. Terraces
Trees or shrubs can be grown alongside soil and conservation structures like terraces or diversion ditches and ridges for the following reasons:
- To stabilize the slope.
- To conserve soil and water.
- To modify the temperature and soil moisture.
- To increase fertility for the benefit of crops.
- To strengthen the terraces through their deep root network which grow into the sub-soil.
- To shelter crops from wind damage.
- To add to the value and diversity of products from the terrace by including fruits and fodder.
AGROFORESTRY PRACTICES
Agroforestry practices are aimed at sustainable land use which helps to achieve high production combined with conservation of resources on which that production depends, thereby maintaining high productivity.
For a land use system to be sustainable, it requires not only the conservation of soil and water but the whole range of resources on which production depends. However, the most basic requirement for sustainable land use is the maintenance of soil fertility.
1. Alley cropping (Hedgerow intercropping)
In this practice, rows of woody perennials are interplanted with annual crops. The woody plants are regularly cut and their leaves and twigs are left on the ground to provide mulch. This litter reduces evaporation, suppress weed growth, and on decomposition, adds organic matter and nutrients to the soil. The main aim of alley cropping therefore is to improve crop yield by increasing soil fertility, controlling weeds and improving the micro-climate. In the course of production, farmers also benefit by obtaining fuel wood, building poles and fodder. Ideally alley cropping tree or shrub should have the following characteristics:
ü The trees should have a sparse and small crown to permit sunlight to penetrate and reach the crops below it.
ü The tree should be able to sprout quickly after cutting or pruning.
ü It should have a deep taproot system to recycle the nutrients and few lateral roots near the surface.
ü The leaf litter should decompose fast to provide the needed nutrients.
ü The tree should be able to fix nitrogen in the soil.
ü It should produce wood, food, fodder, medicine or other useful products for the farmer.
ü The selected trees should be drought and flood resistant.
ü The tree should be able to do well in a variety of soil conditions.
2. Multi-storey cropping
Multi-storey cropping involves a wide variety of woody and herbaceous crops grown together in a dense pattern. Home gardens consisting of plots about a half hectare or less are planted with diverse mixtures of vegetables, fruits, medicinal plants and sometimes fodder grasses. Because of the dense litter and ground cover all the year round, erosion control is very effective. The success of home gardens can be attributed to the following activities:
v Intensive intercropping using various vegetables and other herbaceous crops to spread the risk of crop failure.
v Occasional watering of the plants using either waste water or water harvested from the compound during a heavy downpour.
v Soil enrichment using refuse wastes from home kitchen and livestock wastes.
v Intensive gardening because of availability of labour considering the small size of the plot to be taken care of.
v Erosion control by dense ground cover and canopy is very good.
v Protection of the garden from livestock and wildlife by a living or artificial fence.
3. Woodlots in farms
Farmers can establish woodlots anywhere in their farms to provide them with fuel wood, fodder, building materials and other products.Permanent woodlots, once established, become part of the landscape features and acquire many qualities similar to a forest.
HARVESTING TREES
There are different methods of harvesting trees depending on the initial purpose of establishing them. Most harvesting methods are aimed at managing the agroforestry trees. Different tools such as panga, axe, saw (power or manual) are used to harvest trees.
a. Felling
Felling is cutting down a tree close to the ground. In agroforestry all trees planted at the same time can be felled if all of them have reached the intended maturity stage. Selective cutting of trees may be done leaving some to grow for certain purposes like providing shade for livestock in a pasture, acting as windbreaks, for soil erosion control on grass strips or to provide fodder in a rangeland. All the trees felled are prepared accordingly by removing branches and cutting them to size, before sawing for timber or for use as poles for construction.
b. Coppicing
Coppicing is a management practice applied when harvesting trees. Young and vigorously growing trees are cut at a clean angled cut about 30 cm above the ground. The young trees are left on the ground to drop their leaves which decay to provide organic manure. The dry branches can later be collected for various uses e.g firewood. The stool left will soon sprout to produce new growth.
c. Pollarding
In pollarding the entire tree crown is cut off leaving only the tree trunk. This method also promotes a vigorous multistem regrowth at a higher storey than in coppicing. The harvested tree branches can be used for various purposes.
d. Lopping
Established trees can be lopped by cutting excessive branches to maintain only the required crown size. Lopping as a practice helps to manage agroforestry trees so that the foliage does not excessively shade the crops and interfere with their growth and yield.
e. Pruning
Some agroforestry trees are pruned by cutting selected branches and shoots. Pruning is a technical operation and the farmer must know which branches or shoots to remove. Pruning is done to reduce overbearing of fruits, open up the tree for easy spraying and to have a micro-climate which is not conducive to the development of fungal diseases. Pruning involves removing of soft foliage, small twigs, dead, diseased or curved branches or shoots. Tools used in pruning include a pair of secateurs, pruning saws, or pangas. Prunings can be used for various purposes including mulching, fodder, fuel wood, or composting manure.
CHALLENGES TO AGROFORESTRY
1. Lack of developed markets for products
2. Competition between trees, crops and animals
3. Lack of demonstration sites
4. Lack of training or expertise
5. Lack of knowledge about where to market products.
6. Lack of infrastructure.
7. Insufficient land.
8. Lack of seed/seedling sources.
9. Access to high quality planting material of proven suitability remains a challenge, especially at the start of a farmer-tree planting phase of a landscape.
10. There is lack of reward mechanisms for environmental services provided by agroforestry and plantation.
PASTURE GRASSES AND FODDER CROPS
INTRODUCTION
Grassland is a plant community in which pasture grasses, legumes, sedges and forbes are found with little to no tree cover. The grasslands are classified on the basis of whether natural grasslands or ley grasslands. Other classification is on the basis of life forms, water/moisture requirement.
Natural grassland
This is divided into five zones, namely:-
Zone I. Coastalgrassland.
Zone II. Low tree, high grasslands.
Zone III. Arid and semi-arid grasslands.
Zone IV. Low tree, low grasslands.
Zone V. Highland grasslands.
- Zone I.Coastal grasslands.
The coastal belt is characterized by low altitude. Grasses in this zone must tolerate high temperatures, high humidity and the shading effect of cashew nuts, mangoes and coconuts. Examples of grasses include:-
- Masai love grass, Rhodes grass, guinea grass (Panicum maximum), congo signal (Brachiariaruziziensis).
Legume species include;-
- Centro (Centrosemapuescens), Tropical nudzu(Puerariaphaceoloides), Njahi(Dolichoslablab).
- Zone II. Low tree, high grasslands.
The area is characterized by high temperatures, low erratic rainfall with an altitude of 300 – 1500m above sea level.
Adaptable varieties in this region include:-
- Acacia, Thatching grass (Hyparrhemiarufa), Horsetail love grass (Chlorisroxburghiana), Masai love grass (Eragrostissuperba), Guinea grass, African fox tail.
Legume species include Leucaena(Leucaenaleucocephala), Stylo (Stylosanthesscabra).
- Zone III. Arid and semi-arid grasslands
Grasses found here can tolerate low erratic rainfall and high temperatures. The type occupies about 80% of the country. Grasses spring up at the start of rains and complete their cycle within a very short time of the year. They grow in tufts. They include:-
ü Horsetail grass, Maasai love grass, African foxtail, Guinea grass, Acacia etc
4. Zone IV: Low tree, low grass grassland
· Altitude is 1800 – 2300 m above sea level.
· Areas include Naivasha and Laikipia.
· The area is characterized by low temperatures and low unreliable rainfall.
This is the region of most economically important grasses which include:-
ü Combretum, Red oat grass, Themedatriandra, Rhodes grass (chlorisgayana), Nandi setaria (setariasphacelata), Congo signal (brachiariaruziziensis), Star grass (cynodondactylon)
Legume species found in this area are;-
ü Silver leaf desmodium (Desmodiumuncinatum), Green leaf desmodium (Desmodiumlutortum), Sesbania (Sesbaniasesban), Lucerne (Medicagosativa), Sweat lupin(Lupinusalba).
Most of the pasture improvement that has gone in this country has concentrated in this because it is suited for mixed farming.
5. Zone V: Highland grasslands
- Areas such as Molo.
- Altitude is 2300 – 3000 m above sea level.
The grasses in this zone are characterized by low temperatures and high reliable rainfall. Predominant grasses include:-
ü Kikuyu grass ( pennisetumclandestinum, Oats (avenasativa), Perennial rye grass (loliumperenne), Cocks foot (dactylic glomerata),Manyatta grass (eleusinejaegari) – this type in areas tending towards zone 4 supports a lot of dairy farming in the country.
Legume species include;-
ü Vetch (Viciasativa), white clover (Trifoliumsemipilosum), lupins (Lupinusalba).
Tropical and sub-tropical natural grasslands are predominant in the natural grasslands. The distribution of natural grasslands is influenced by:-
i. The amount of rainfall and its distribution.
ii. Temperature.
iii. Soil types.
iv. Salinity.
v. Solar radiation.
vi. Relative humidity.
The amount and distribution of rainfall influences the structure and composition of the natural grasslands. Soil moisture has an influence and therefore shows a wide seasonal variation on the basis of amount and distribution. These natural grasslands provide ideal habitat for many animals such as the herbivores, carnivores and micro-organisms. The patterns of growth are due to climatic and fertility factors which can be induced by cutting either through grazing, mowing and the various fertilizers to create habitats that are used for grasslands.
GRASSLAND IMPROVEMENT PROGRAMS
They include:- i. Forage collection.
ii. Forage introduction.
iii. Forage evaluation.
Forage collection, introduction and evaluation is the first major discipline in the grass programme with the following objectives:-
i. Collection and evaluation of pastures including assembling and maintaining suitable forage species from either local areas or introducing species from areas with similar agro-ecological zones.
ii. To improve on the genetic potential of the identified forage species through selection and breeding i.e creating and implementing pasture gene bank for plant material.
iii. To establish suitable cultural practices for pasture development, management and utilization & conservation.
iv. Evaluation of collected, introduced forage germplasm with particular reference to their usefulness in forage improvement.
v. Multiply the promising forage species and carry out on-farm trials and to further test the suitability of the forage materials in various agro-ecological zones.
Plant introduction, collection and evaluation is a continuous process that allows the regeneration of new plant germplasm from local or exotic origin over the years. Many grasses, legumes, fodder trees and shrubs have been collected or introduced from outside the country and have contributed to the development and improvement of grassland in Kenya. The majority of this forage germplasm have undergone initial screening, testing and evaluation and the promising types isolated for further multiplication.
Some of the species that are still given attention include:-
ü Rhodes grass, Nandi setaria, Kitale molasses, Star grass, Congo signal
Fodders include:
ü Napier grass, Guatamala grass, Giant panicum, Giant setaria
Temperate grasses include:
ü Cocks foot, Perennial rye grass, Italian rye grass oats
Legume species include:
ü Greenleaf desmodium, Silver leaf desmodium, Kenya white clover, Red clover, Lupines, Glycine.
Forage crops include:-
ü Sweet potatoes (ipomeabatatus)
Forage is a term widely used to cover grasses, legumes, fodder trees& shrubs and Forbes.
Forages therefore are compared in terms of establishment, management, conservation and utilization.
LIFE FORMS CLASSIFICATION
Classification of grasses based on life forms is categorised into three forms. Namely:-
a) Annuals – These grasses germinate, grow and complete their life cycles in one season.
b) Biennials – They germinate, grow and complete their life cycle in two seasons.
c) Perennials – They grow and complete their life cycle in more than two seasons.
WATER REQUIREMENT CLASSIFICATION
i. Xerophytes – grow in arid and semi-arid conditions. They have adaptations to live in harsh environments such as needle-like leaves to reduce evapotranspiration.
ii. Mesophytes – grow in wet areas.
iii. Hygrophytes – grow in mashes.
iv. Hydrophytes – grow in water.
PERMANENT OR TEMPORARY LEYS.
Permanent grasses will grow for more than four years, while temporary leys will grow for less than four years and mostly grown in a rotational basis. Ley grass is established by use of seeds and easier to destroy. Examples include:-
ü Rhodes grass, Setaria, Brachiaria, Guinea grass, Coloured guinea (panicumcoloratum)
Seed of ley grass are available in commercial scale.
METHODS OF PASTURE ESTABLISHMENT
The methods used are largely dictated by the prevailing environmental conditions and their demand for grazing.
1. Direct drilling
· This method involves land preparation to the required tilth and compaction that is fine and firm.
· Seeds are then mixed with phosphatic fertilizers at the rate of 40-60 kg of p2o5/ha.
· Seeds are then drilled or broadcasted. If seeds are drilled, a carrier such as saw dust is necessary to make the seed flow freely.
· Direct drilling is recommended when rain is expected and for the first growing pastures such as Rhodes grass.
· The developing seedlings should be kept free from weeds by use of 2,4-D amine,72% at 1.5 litres/ha.
· A new stand is ready for grazing in 3 – 4 months.
The success or failure of the establishment phase is influenced by the following:-
i. Choice of species.
ii. Provision of favourable environment for germination and seedling development.
iii. Use of compatible species when planting grass legume mixtures.
iv. Seed treatments and inoculation.
v. Physical loss of seed by harvesting.
vi. Ants or physical movement of seeds by water.
vii. Mortality of emerged seedlings because of environmental stresses.
2. Under sowing
This is planting of pasture species under a nurse crop such as maize, wheat and sunflower.
When maize is used as a nurse crop, pasture seeds are mixed with phosphatic fertilizers at the rate of 40-60 kg/ha and then broadcasted after the second or final weeding.
At the end of the growing season, the arable crop is harvested.
Weeds are then cut back and Stover removed from the field to reduce the shading effect over the developing pasture seedlings.
If wheat is used as a nurse crop, the variety selected should be short but with strong straw. Wheat is drilled in rows 15 cm apart and then pasture seed is mixed with phosphatic fertilizer and drilled at the same time with wheat. After harvesting wheat, the sole pasture establishes.
Under sowing is recommended in the final year of an arable crop and when early grazing is not expected.
3. Over sowing
This is the introduction of improved pasture species into unimproved grassland. Before introducing the pasture species, it is important to reduce the existing vegetation cover by any of the following methods:-
i. Intensive grazing.
ii. Burning.
iii. Mowing and racking the existing vegetation cover.
iv. Use of herbicides such as round-up.
v. Strip ploughing.
Grazing should be delayed until the introduced species has established properly. Pastures should be top-dressed at the beginning of rains using 100kgN/ha or 10 tons of FYM per ha depending on whether it is pure grass stand or grass legume mixture regime.
Under stocking or low grazing interval encourages undesirable plant species to invade and replace the desired pasture species.
The grazing of new pasture should be done at the booting or early flowering stage when the pasture quality is high.
Subsequent grazing should be done at two monthly intervals depending on the species.
Different grazing systems are adopted to suit the local situation.
The quality of the available feed to greatly extend depends on the species and in general, legumes have higher nutritive value than grasses. Legumes also maintain the quantity more than the grasses.
FODDER CROPS
Fodder crops are defined as annual or perennial crops cultivated on arable land and are cut and carried to the livestock. Fodder crops are usually grown in rotation with other arable crops. They are characterized by dry matter (DM) yield of high digestibility prepared to pasture grasses.
The main fodder crops used include:-
ü Napier grass ( Pennisetumpurpureum), Sorghum, Guatamala grass (Tripsacumlaxum), Giant panicum( Panicum maximum), Giant setaria ( Setariasplendida), Edible cana (Canna edulis),Lupins (Lupinus alba), Lucerne (Medicagosativa), Oats (Avenasativa), Brassica (Turnips, swedes, Radish, marigolds, Fodder beets, Kales etc)
FODDER ESTABLISHMENT
Land should be prepared during the dry season to ensure that rhizomatous weeds are got rid of. The spacing of fodder depends on species and the area fodder is to be established. For example,
1 .Napier grass
i. Spacing for Napier grass is as follows:-
- 0.5 x 0.5 m or 1.0 x 0.5 m in wet areas.
- 1.0 x 1.0 m for medium potential areas.
- 1.5 x 1.0 m for semi-arid areas.
ii. Climatic requirements
- Altitude – 0 – 2100m above sea level
- Rainfall – high rainfall of 1200mm/year.
- Fertile soil.
- Wet weather.
iii. Varieties of Napier grass
-French cameroons, Ex-meru, Bajra, Clone-13, Bana grass, Ex- Limuru, Uganda hairless.
iv. Land preparation & Planting
Napier grass should be planted in a well prepared seedbed free from Rhizomatous weeds such as couch grass (Digitariascalarum), Kikuyu grass (Pennisetumclandestinum), Nut grass ( Cyperusrotundus).
It can also be established by inter-planting in maize crops after the final weeding.
Napier grass can also be intercropped with legumes such as silver leaf or green leaf desmodium. The inoculated legume should be broadcasted at the same time as the Napier grass is planted.
· Planting materials
Napier grass is established using canes with 3 – 4 nodes, root splits or whole stem. Root splits establish faster than canes and whole stems but are not readily available. When canes are used for establishment, it is important to ensure that 2/3 of the cane is buried at an angle of about 45o.
· Spacing
The closer spacing is suited for high rainfall areas and there is demand for more planting material than the wider spacing.
Wider spacing is suited for semi-arid environment and there is a reduction for competition for moisture.
· Fertilizer requirements
Fertilizer rates of 40 – 60 kg of P2O5/ha is recommended at planting.
v. Field management practices.
- Weeding especially after cutting Napier.
- Top-dressing with 60 – 80 kg of N/ha preferably when it is wet.
vi. Harvesting.
The productive life of Napier grass depends on management but maximum yields are usually achieved during the first four years. The grass does not have major diseases within the first four years of the lifespan although show mould fungus is reported as a problem of Benioswkiaspareoides. The fungal infection is particularly acute for French Cameroon.
Napier grass is difficult to eradicate when not required but if it is grazed directly, particularly during dry season, and followed by immediate ploughing it can be eradicated.
Under normal circumstances, grazing the crop is not recommended because it weakens the root system of the crop. It is recommended that Napier is left 2-3 months before the onset of the dry season to ensure there is sufficient quantity of dry matter to cater for dry season. If the crop is left uncut for more than 3 months, it becomes stemmy and unpalatable.
The grass should be cut at the onset of rainy season, weeded and top-dressed to enable it to produce sufficient dry matter.
2. Guatamala grass
· It is a perennial fodder which grows between 0 – 2300 m above sea level.
· It is slow to establish and has a weak rooting system.
· It has a high yield to stem ratio compared to Napier grass.
· It is highly digestible.
· The grass should not be grassed on directly but should be cut and carried to livestock.
· This fodder is easily eradicated if not required.
3. Oats.
· Oats are recommended in high altitude cool areas i.e 2000-3000m above sea level.
· It can be grown in pure stand or in mixture with vetch ( Viciasativa).
· Varieties of oats include:- Sure grain, Jasiri and Lampton 518.
· Planting :-
The seeding rates are 70-80 kg/ha for pure stand and 40 kg/ha for mixed stand.
The seed should be mixed with fungicide and insecticide before planting to prevent further diseases and insects.
The seed can either be broadcasted or drilled and fertiliser applied at the rate of 40-60kgp2o5/ha.
After harvesting, the crop should be top-dressed at 20-30 kg of N/ha to enhance growth and subsequent yield of fodder.
4. Fodder Maize
Sometimes fodder maize is also grown as high energy rich crop.
It is suited in areas between 1500 – 2300 m above sea level.
The most complete utilization of fodder maize is inform of silage especially if the crop is harvested at dough stage i.e after the milk stage but before the grains harden.
Small scale farmers in high potential areas grow the crop continuously throughout the year and feed the livestock without having to make silage.
5. Sweet Potatoes
Sweet potatoes provide energy for both livestock and humans. It is utilized as either vines or tubers. Vines are a good source of proteins and roughages. Sweet potatoes grow well on fertile soils with a PH of above 5. They should not be grown in areas where night temperatures fall close to 0oC because the vines are affected and turn brown. Cuttings or tubers can be used as planting materials but vines are more available than tubers. 2/3 of vines should be covered with soil at planting. Spacing of 50-60 cm is used. The plants can be harvested after every four months leaving stubble of 15 cm for quick vine regrowth. Planting material should be dipped in an insecticide to prevent sweet potato weevil. Fertilizer at the rate of 40-60kg P2O5/ha or manure of 10 tons should be used during planting.
Sweet potato varieties
ü Musinya, mukunungu&Namunjuna are mainly for vines.
ü Bisale&Omito are for tubers.
ü Muibia is a dual purpose crop.
6. Sorghum.
This is a drought tolerant fodder that is suitable for arid & semi-arid areas. The varieties commonly grown include:-
ü Velvet sorghum.
ü Sudan grass.
ü Columbus grass.
ü E 6508 (cold tolerant).
Establishment.
Seed rate of 20-30kg/ha is recommended in rows of 17-30 cm apart in wet conditions.
Seed rate of 5kg/ha is drilled at 100cm apart in arid areas.
At the time of planting, 40-60kgP2O5/ha fertiliser is required. The growth should be established in a seed bed free from weeds.
GRAZING MANAGEMENT
Objectives of grazing management
i. To maintain high production of a good quality herbage for the longest possible period.
ii. To maintain a favourable balance between a favourable species.
iii. To achieve efficient utilisation of the herbage produced by conserving excess herbage at the peak of the growing season.
iv. To achieve high annual production in terms of milk, meat, wool and hides& skins from the herbage.
GRAZING SYSTEMS
1. Continuous grazing
2. Rotational grazing
3. Zero grazing
4. Semi zero grazing
5. Tethering
CONTINUOUS GRAZING
This is a grazing system where animals are kept in an area continuously throughout the year.
ROTATIONAL GRAZING
Pasture is divided in a number of paddocks and livestock is moved in a regular sequence around the paddock. The number of paddocks is determined by dividing the rotational cycle by the grazing period.
No. of paddocks=rotational cycle/grazing period.
If the rotational cycle is 20 days, and animals stay for 4 days in each paddock, then the number of paddocks are 5, that is;-
20/4= 5 paddocks.
If the number of time to complete a cycle is 60 days, where animals stay 6 days, that is;-
No. of paddocks = 60/6 = 10 paddocks.
Rotational cycle is the number of days from the beginning of one grazing period until the beginning of the next grazing period.
The grazing period is the average number of days within a cycle during which each cycle is occupied by grazing animals.
The rest period is the number of days within a cycle when there are no grazing animals in a paddock.
No. of paddocks = Rest period + 1
Grazing period
If the rest period is 54 and then the grazing period is 6, then;-
= 54/6 + 1
= 9 + 1
= 10 paddocks.
The objective of rotational grazing is to utilise the pasture when it is highly nutritious and also allows adequate time for the pasture to regrow.
ZERO GRAZING
This is a term used to describe the practice of cutting fresh herbage carrying it and feeding livestock at a confinement. This may lead to improved use of forage compared to other grazing systems.
Zero grazing is an intensive system used for dairy animals. The stage of cutting forage is important because the nutritive value tends to decrease with maturity of the crop.
Booting stage or initial head emergence is suitable time for pasture grasses because it combines both quality and quantity.
The process of hay making should be turned regularly for it to dry before collecting and baling the material.
NB; There are some terms used in pasture management. These include;-
1. Stocking rate: It is the actual number of animals per livestock unit for high potential and low potential areas respectively.
2. Carrying capacity: This is the maximum number of animals that can survive the greatest period of stress each year on a given land area.
3. Grazing pressure: This is the actual number of animals to forage ratio at a specific time i.e the number of animals per ton of standing forage or hay.
4. Sustainable range: This is the range which is accessible to livestock that can be grazed on a sustainable yield basis without damage to other resources.
SILAGE
Silage is fermented fodder which is stored to feed cows during dry season (preserved herbage). The herbage is preserved in air tight structures called silos. There are different silos such as stack silo, bunker silo, clamp silo, trench silo and pit silo. The most common one is the trench and bunker silos. The crops used for silage making should contain adequate levels of substrates in form of carbohydrates, high dry matter content and should also have ability to resist PH changes. Silage can therefore be made from Napier grass, Sorghum, Maize stems, oats or Sugar Cane tops.
Requirements for silage making
- Chopped forage such as Napier grass.
- Molasses.
- Water.
- Silage plastic bag.
PROCEDURE OF MAKING SILAGE.
1. Collect the Napier grass after it is chopped and put it onto a plastic sheet on the ground. Do this where you plan to store the bags as they will be heavy.
2. Mix 1 kg of molasses with 3 kg of water in a watering can.
3. Sprinkle the molasses-water mixture onto the cut Napier grass and mix well.
4. Put the mixed Napier and molasses and water into a silage bag.
5. Press down to make sure no air is left in the bag. If there is air, then it will not ferment well.
6. Tie the top of the silage bag tightly with sisal twine.
7. Put stones or rocks on the tied bag to ensure it is pressed down.
8. Store somewhere dry and out of the sun.
9. Ants, rats and birds will be attracted to the silage so check the bags often.
10. It will be ready in 8 weeks but it can be stored for a lot longer and used to feed cows during the dry season.
Qualities of good silage
ü PH level of 4.2.
ü Sweet smelling.
ü Yellowish green in colour.
NB; the quality of silage made depends on the species of the crop, type of silo, the chop length and the prevailing temperature.
HAY
Hay is grass, legume or other herbaceous plants that have been cut, dried and stored for use as animal fodder. Hay can be used as animal fodder when or where there is not enough pasture or rangeland on which to graze an animal, when grazing is unavailable due to weather.
Commonly used plants for hay include legumes such as alfalfa, lucerne and clovers. Oat, barley and wheat plant materials are occasionally cut green and made into hay for animal fodder.
HAY MAKING
i. Hay plant materials are harvested or cut when the seed heads are not quite ripe and the leaf is at its maximum by use of a mower or a swathe machine designed to cut hay.
ii. The cut material is the allowed to dry so that the bulk of the moisture is reduced to about 15 – 20% moisture content.
iii. The cut plant materials are then raked into long, narrow piles known as windrows and baled ready for storage by use of a baler machine.
iv. The bales are then stored under a shade to prevent rotting and moulding due to wet conditions.
STANDING HAY
This is a practice where a farmer plants grass and it is kept until times of need especially in dry season when the pastures are utilised by being cut and fed to the animals or allowing animals to graze on it directly, depending on the pasture species.
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